Parexel International Corp., which provides such services as helping pharmaceutical companies get their experimental drugs to market, said it is creating a special unit that will focus on small and mid-sized companies.

For much of its roughly 30-year history, Waltham-based Parexel has gotten a big chunk of its revenues from large drug companies around the world. Among other sevices that it provides, Parexel helps its drug-company customers to navigate the clinical-testing process needed to win regulatory approval of their products.

But as the drug industry has shifted, the landscape is changing. Citing industry data, a Parexel press release noted that “small and mid-sized companies are the engine of the biopharmaceutical industry, with 81 percent of ongoing development programs originating from sponsors outside of the top 25 biopharmaceutical companies.”

The new Parexel BioPharm unit is designed to let smaller companies know that not only does Parexel welcome their business but that it also has a good deal of experience in providing services that are specially tailored for smaller drug companies.

Parexel operates in 50 countries around the world and has 11,920 employees. For its fiscal 2011, the company reported total service revenue of just over $1.2 billion.