Arriving for his last lecture at the Boston University School of Public Health in May, Dr. William J. Bicknell swept across the stage on a Segway.

The audience stood and applauded as he grinned and waved, a red helmet strapped tightly on his head, and a deep purple bruise across his left eye hinting at a recent crash into the wall of his kitchen.

Voice strong and passionate, he ticked off lessons from a lifetime in public health, blasting arrogance in decision-making and heralding the potential to reduce suffering through good policy and wise spending. Some colleagues had a pool going for how many times he would use a choice profanity.

“Bad public health kills,” he told the audience. “In a low-income country, it’s life and death for someone we’ll never know, but if we spend it wrong, we kill them.”

Dr. Bicknell, who founded BU’s Center for International Health and formerly served as state commissioner of public health, died of metastatic lung cancer June 5 in his Marshfield home. He was 75 and, his family noted, had never smoked.

“Bill was larger than life,” said Dr. Ayo Ajayi, a former student of Dr. Bicknell’s who is now vice president for field programs at the global health nonprofit PATH. “He was completely irreverent. … He was always true to himself and he had a huge heart. He has so many friends because everyone is special to him.”

His colleague Susan Foster, a professor of international health at BU, called Dr. Bicknell “one of the giants” in his field.

“He’s been such a huge force at BU,” she said. “He really got the department started.”

Dr. Bicknell’s persistence and love of the landlocked African country of Lesotho fueled BU’s support for the Lesotho-Boston Health Alliance. He and Dr. Brian Jack, associate professor of family medicine at BU, cofounded the alliance to battle AIDS by improving hospitals and education for doctors and nurses in the nation of 2 million.

“He was my good friend and a trusted colleague and mentor, and his heart was with the people of Lesotho, to make their lives better,” Jack said in an announcement of Dr. Bicknell’s death on BU’s website.

Ajayi, who is from Nigeria, credited Dr. Bicknell with launching his career when he walked into his office in 1980.

“I was the first international student they had. He told me, ‘There’s not much for you here, but we’ll just have to put something together then,’ ” Ajayi recalled. “He taught me most of what I know in public health.”

Reflecting on the loss of his mentor and the irony of his death from lung cancer, though he never smoked, Ajayi noted that Dr. Bicknell’s vice was salt. He carried a salt shaker in his pocket at all times.

After his cancer diagnosis in 2010, Dr. Bicknell traveled the world to see friends and further strengthen the Lesotho-Boston alliance, last visiting Lesotho in March. He also traveled to South Africa and Indonesia and posted details of his treatment online.

“Pills and technology help,” he wrote. “But friends and family count a lot more.”

The youngest of three siblings, Dr. Bicknell grew up in the Waban section of Newton.

In 1958, he graduated from Johns Hopkins University with a bachelor’s degree in biology. Four years later, he graduated from Duke University’s School of Medicine and joined the US Public Health Service Commissioned Corps, for which he was senior physician for Peace Corps volunteers in Ethiopia.

“That’s when he decided he didn’t want to be a surgeon. He wanted to go into public health,” said his wife, Jane Hale, an associate professor of French and comparative literature at Brandeis University.

They met on a blind date and were married 18 years.

“Everybody thought I was crazy,” she said of marrying someone who had been married before. His marriages to Jean Bicknell, Jennie McFarland, and Freya Olafson ended in divorce.

“Don’t worry,” he told Jane, “you’re my last and best.”

They had bonded over shared Peace Corps experiences and tales of academia. She had taught at a school in Chad.

“I thought it would be fun and it was,” she said of their marriage. “We had a wonderful ride.”

During his last lecture, Dr. Bicknell poked fun at his romantic life, playing one of his favorite songs, “Every Day is Ladies’ Day With Me,” from a musical his father took him to see when he was a teenager.

Then he played Johnny Cash’s “Folsom Prison Blues,” a tune that signaled to students it was time to start class.

A service has been held for Dr. Bicknell, who in addition to his wife leaves two sons, Richard of Santa Clara, Calif., and Christopher of Buxton, Maine; a brother, Richard of Port Orange, Fla.; and two grandsons.

In 1972, Governor Francis W. Sargent appointed Dr. Bicknell state commissioner of public health.

Dr. Bicknell soon faced a public health crisis when evidence of the toxic algae known as red tide was found off Cape Ann. He lobbied the governor for an aggressive response even before the final lab results were finished. Fish markets were shut and shellfish stocks were destroyed to protect diners.

The shellfish industry was outraged. The state’s response, however, was credited with keeping the number of injuries low.

About two dozen people became sick from eating clams. Tests eventually confirmed the worst red tide outbreak in state history and shellfish harvesting was shut down from Maine to Long Island Sound.

Dr. Bicknell also had served as medical director of health and retirement funds for the United Mine Workers of America and had been acting director of the neighborhood health center program for the US Office of Economic Opportunity.

He joined the BU faculty in 1978 and usually began each semester with dueling interpretations of public health: “The art and science of deciding who dies, when, and with what degree of misery,” versus, “The art and science of deciding who lives a longer, less miserable, happier life.”

In his May lecture, he told a favorite story about retrieving ripe melons nightly from a dumpster near his state offices in the 1970s.

A janitor confronted him and said elderly women in the neighborhood relied on those discarded fruits and vegetables from a nearby fruit stand for their food. From then on, Dr. Bicknell said, he always made a point of remembering “the melon lady.”

“I always think of the melon lady, the person at the table who isn’t there, and she’s my guy when it comes to decision-making,” he said.