A research and consulting company with a large presence in Bethesda has landed multimillion-dollar contracts to study the long-term health effects of military service on Vietnam veterans, market U.S. government substance abuse and mental health programs, and evaluate federal training and employment programs.

A three-year, $6.6 million contract with the Department of Veterans Affairs will pick up where the National Vietnam Veterans Readjustment Study left off in 1986 and 1987, said William Schlenger, a principal scientist at Abt Associates of Cambridge, Mass., and director of the new study. Schlenger also worked on that earlier study when he was with Research Triangle Institute in North Carolina, which has a Rockville office.

The new survey, called the National Vietnam Veterans Longitudinal Study, will delve into questions such as whether combat-related post-traumatic stress disorder relates to chronic physical illnesses, and will have a critical bearing on veterans fighting in Iraq and Afghanistan along with those who served in Vietnam, he said.