To compile and analyze critically the literature published on street children and substance use in resource-constrained settings. We searched the literature systematically and used meta-analytical procedures to synthesize literature that met the review's inclusion criteria. The significant gaps in the literature, including a dearth of data on physical and mental health outcomes, HIV and mortality in association with street children's substance use. Street children from resource-constrained settings reported high life-time substance use. Inhalants are the predominant substances used, followed by tobacco, alcohol and marijuana.