This study highlights the utility of partner typologies for examining young women's STD/HIV risk perception and sexual risk-taking behavior. Study data from quantitative sources identify general trends in perception and behavior among young women but reveal little about the influence of partner characteristics. Qualitative data analysis produces nine 'super categories' to examine the influence of partner characteristics on the outcomes of interest. These categories reveal the influence of relationship expectations, emotional commitment, and 'trust' on STD/HIV risk perception and risk-taking behavior; more detail than provided by conventional categories such as 'regular' and 'occasional' partners. Study results indicate opportunities for intervention and suggest that future research should examine partner categories used in major quantitative surveys to determine their ability to reveal differences in self-protective behavior with different partners. Such information can enhance public health efforts and make STD/HIV prevention programs for young women more target-specific and, ultimately, more effective