There is a paucity of research on the psychosocial and behavioral characteristics of individuals who inject methamphetamine (meth). The present study compared injection and non-injection users of meth in terms of background characteristics, drug use patterns, health and social problems, sexual risk behavior, and psychosocial factors. The sample consisted of 194 HIV+Men who have Sex with Men (MSM) who were enrolled in a sexual risk reduction intervention for meth users. Men who injected meth were significantly more likely to be Caucasian, bisexual, homeless, divorced/separated, with lower educational attainment as compared to non-injectors. Injectors also reported more years of meth use, greater frequency and amount of meth use, more social and health problems, including higher prevalence of STDs and Hepatitis C, and more sexual risk behaviors. In terms of psychosocial factors, injection users of meth scored significantly higher on measures of impulsivity and experiences of rejection, and lower on a measure of emotional support. A multivariate logistic regression revealed that educational attainment and experiences of rejection were the factors that best discriminated between injection and non-injection users of meth. The unique characteristics of injection meth users are discussed in relation to the development of effective HIV prevention programs for the target population.