A sample of 301 Philadelphia adolescents were assessed for substance use and place-based social network quality, a weighted variable based upon risky and protective behaviors of alters. The network measure was anchored in routine locations identified as safe, risky, important, or favorite. Results show young females' (13-16) substance use was strongly associated with their place-based social networks compared to older females (17-20) and compared to young and older males. Younger females' protective networks reduced their likelihood of substance use compared to females with risky networks (OR=.94, CI=.89-.99, p<.05), while young males experienced no protective network effects. Older females' protective networks reduced the likelihood of substance use compared to those with risky networks (OR=.96, CI=.93-.99, p<.005). Older males' protective networks also reduced their likelihood of substance use (OR=.86, CI=.74-.99, p<.05). Results highlight the varying affects of place, gender, and age on adolescent social network protection and associated risk for substance use.