The purpose of this study was to examine the attitudes about hypothetical human papillomavirus (HPV) vaccines in two groups of women in clinical settings. Twenty adolescent women attending an urban community adolescent health clinic and 20 adult women attending a city health department sexually transmitted disease (STD) clinic were recruited to participate in individual interviews. Adolescents were 14-18 years of age (mean 15.6), 75% nonHispanic white, and 75% sexually experienced. Adults were 20-50 years of age (mean 33.6), 95% African American, and all were sexually experienced. As part of the interview, participants ranked nine hypothetical HPV vaccines in order of acceptability. Each vaccine was uniquely defined as a function of cost ($150, $50, or free), efficacy (50% or 90%), disease targeted (genital warts, cervical cancer, or both), and physician recommendation (not mentioned by a physician or specifically recommended). Rankings by adolescents and adults were highly concordant (Spearman rho = 0.9). Efficacy, physician's recommendation, and cost influenced rankings most strongly. Ranking decisions were often based on complex decision making, in which all characteristics were considered simultaneously. These findings suggest that certain features of an HPV vaccine might significantly affect vaccine acceptability. Vaccine efficacy, physician endorsement, and cost were particularly salient issues.