Types of drugs used and routes of administration were assessed, and correlations to social affiliation, HIV status, and lifestyle stability were explored among 672 street-recruited drug users in Baltimore. Participants reported 63 patterns of drug use, which were categorized into five groups: (1) only sniff heroin; (2) smoke crack and may snort cocaine; (3) sniff heroin and smoke crack; (4) inject heroin and cocaine; and (5) inject heroin and cocaine, smoke crack, and may snort heroin. Social network analysis revealed that heroin sniffers and crack smokers both tended to associate with those with similar drug use patterns. High symptoms of drug dependence were observed among heroin users irrespective of mode of administration. Injectors reported higher rates of hospitalization compared to noninjectors even after adjusting for HIV status. Implications to HIV prevention and drug use transitions are discussed.