We examined crack use in a cohort of methadone patients originally enrolled in 1984-86. Crack use questions were added to the study in 1987. Of the 494 methadone patients originally enrolled, 228 subjects remained in methadone and were re-interviewed in 1987-88, and 234 remained in methadone and were re-interviewed in 1988-89. Approximately one-quarter of the subjects were using crack at each of the 1987-88 and 1988-89 data collection points, and only 3% of the subjects were using crack at daily or greater frequencies at each of the 1987-88 and 1988-89 interviews. Concurrent crack use was associated with (a) the number of noninjected drugs being used; (b) the number of IV drug-using sexual partners; (c) drug injection; and (d) the use of nonheroin opiates. Persistent crack use, defined as use in both 1987-88 and 1988-89, was associated with previous noninjected drug use and previous suicide attempts. While the potential problem of crack use among methadone patients should not be minimized, it appears that, compared to illicit drug injectors not in treatment, being in methadone maintenance may offer a protective effect against crack use.