The present study sought to identify demographic, structural, behavioral, and psychological subgroups for which the Antiretroviral Treatment Access Study (ARTAS) intervention had stronger or weaker effects in linking recently diagnosed HIV-positive persons to medical care. The study, carried out from 2001 to 2003, randomized 316 participants to receive either passive referral or a strengths-based linkage intervention to facilitate entry into HIV primary care. The outcome was attending at least one HIV primary care visit in each of two consecutive 6-month periods. Participants (71% male; 29% Hispanic; 57% black non-Hispanic), were recruited from sexually transmitted disease clinics, hospitals and community-based organizations in four U.S. cities. Thirteen effect modifier variables measured at baseline were examined. Subgroup differences were formally tested with interaction terms in unadjusted and adjusted log-linear regression models. Eighty-six percent (273/316) of participants had complete 12-month follow-up data. The intervention significantly improved linkage to care in 12 of 26 subgroups. In multivariate analysis of effect modification, the intervention was significantly (p < 0.05) stronger among Hispanics than other racial/ethnic groups combined, stronger among those with unstable than stable housing, and stronger among those who were not experiencing depressive symptoms compared to those who were. The ARTAS linkage intervention was successful in many but not all subgroups of persons recently diagnosed with HIV infection. For three variables, the intervention effect was significantly stronger in one subgroup compared to the counterpart subgroup. To increase its scope, the intervention may need to be tailored to the specific needs of groups that did not respond well to the intervention.