The number of deaths due to AIDS in high-risk populations continues to increase. Nationwide approximately 25 percent of AIDS patients are intravenous (IV) drug abusers, and it is very likely that an increasingly larger number of AIDS patients receiving AZT therapy will have had a history of IV drug abuse. The major chemical treatment for IV drug abuse is daily methadone maintenance therapy, and IV drug abusers who are HIV positive represent a large number of patients who will undergo long-term treatment with both methadone and AZT. Therefore, the study of potential drug interactions is essential.