To determine the compliance and tolerance with zidovudine (azidothymidine or AZT) therapy among poor, minority, and intravenous drug-using patients, data were collected on all AIDS and ARC patients followed for at least 4 weeks in a New York City Human Immunodeficiency Virus clinic. Ninety-nine patients received zidovudine, of whom 75% were males, 92% were minorities, and 59% had a history of intravenous drug use. Of the 99 patients, 72 had AIDS and 27 had ARC with T-helper (CD4) lymphocytes less than or equal to 500 mm3. Eighty-seven of the 99 patients (88%) were compliant with zidovudine therapy. Fifty-seven percent of these had at least one adverse drug reaction requiring dose reduction (44%) or cessation (13%). Adverse reactions were similar to those reported in other populations with HIV-related illness, although headache and nausea were less common. Twenty opportunistic infections (OIs) or HIV-related malignancies occurred in 15 of 82 (18%) patients who were on zidovudine for at least 4 weeks (7.6 OIs/1,000 patient weeks). Seven of the 82 died (9%), compared to 9 of the 17 patients (53%) who did not complete 4 weeks of zidovudine therapy (p less than 0.05). There were no significant differences in any of these measures when intravenous drug users were compared with other risk groups. We conclude that zidovudine can be administered to intravenous drug users and others in an inner city clinic with acceptable compliance and tolerance.