Designing interventions to reduce HIV transmission among injecting drug users (IDU) requires reliable estimates of risk behaviors. We present population-based estimates for unsafe injection practices and sexual risk behaviors among male IDUs recruited through respondent driven sampling in India (Delhi: 783; Imphal: 766). IDUs in Delhi, mostly street-based (68%), reported injecting pharmaceutical agents and a greater frequency of injections/day. IDUs in Imphal, mostly home-based (98%), used heroin/opioids and injected less frequently. Needle sharing was common (Delhi: 33%; Imphal: 43%). Sixty-five percent of IDUs in Delhi and 55% in Imphal were sexually active during the previous year. Multiple sexual partners were more frequent in Delhi (49% vs 21%); IDUs in Imphal reported more regular sex partners (82% vs 44%). Consistent condom use with regular partners was extremely low (Delhi: 8%; Imphal: 19%). HIV testing was infrequent (Delhi: 37%; Imphal: 49%). IDUs are a heterogeneous group with different prevention needs requiring need-based tailored prevention interventions.