This article reports the first meta-analysis of the literature on protection motivation theory (Rogers, 1975, 1983; Rogers & Prentice-Dunn, 1997), a model of disease prevention and health promotion that has generated research for over two decades. The literature review included 65 relevant studies (N= approximately 30,000) that represented over 20 health issues. The mean overall effect size (d+= 0.52) was of moderate magnitude. In general, increases in threat severity, threat vulnerability, response efficacy, and self-efficacy facilitated adaptive intentions or behaviors. Conversely, decreases in maladaptive response rewards and adaptive response costs increased adaptive intentions or behaviors. This held true whether the measures were based on intentions or behaviors, and suggests that PMT components may be useful for individual and community interventions.