This study examined the extent to which social relationships were associated with continued injection drug use and needle sharing among 252 methadone maintenance patients. Logistic regression analyses indicated that drug use was highest among persons who had a substance using live-in partner and among those with more drug-using social relationships. Among injectors, whites and those who had more people present during IV drug use were more likely to share needles, while those with more emotional support were less likely to do so. These findings suggest that personal relationships strongly influence continued injection drug use and that methadone programs should help patients develop social networks of non-users.