This paper uses detailed data on prescription drug and other services from the Medical Expenditure Panel Survey (MEPS) to examine recent trends in mental health and substance abuse (MH/SA) treatment between 1996 and 2001. While use of ambulatory services remained constant, prescription drug use increased rapidly, with the result that 5.5 million more Americans received treatment in 2001. Prescription drug spending increased at a real rate of almost 20 percent a year. About one-third of this increase came from more MH/SA medication users and two-thirds from higher costs per user.