A national sample of 25,106 out-of-treatment crack cocaine and injection drug users was examined to determine the effect of aging on HIV risk behavior. Injectors and crack cocaine users aged 55 and over were compared to those who were aged 18 to 54 years of age. Results showed that the behavior risk of older persons did not differ substantially from those reported by other age groups, and that injection risk rose steadily along with age for all ages represented in the sample. The authors conclude that older persons who use illegal drugs remain at elevated risk for HIV compared to the general population, and may be in need of more targeted intervention strategies.