This study was designed to assess differences in drug and sex-related risk behaviors between injectors of opiates only, opiate/sedative mix only and stimulants only. Participants were current out-of-treatment injection drug users (IDUs), unaware of their HIV status, recruited through street outreach in Kiev, Odessa and Makeevka/Donetsk, Ukraine. Overall, 22% tested positive for HIV, including 39% among opiate/sedative injectors, 19% among opiate injectors and 17% among stimulant injectors. Despite these differences, stimulant injectors were at higher risk than other IDUs in sharing a used needle/syringe, always injecting with others, injecting a drug solution drawn from a common container, having an IDU sex partner, not using condoms during vaginal or anal sex and on composite measures of injection and sex risks. After controlling for age differences, stimulant injectors remained at higher risk in their needle and sex risk behaviors. Without intervention, it is likely that HIV will increase among stimulant injectors.