Many researchers have examined the influence of perceptions on health related behaviors and efficacy perceptions have been shown to have powerful correlations with health behaviors. Most studies have focused on adults, few have looked at adolescents' efficacy perceptions about their health, and none have addressed the confidence teenagers have in their daily mental and physical health routines. The School Health Efficacy Questionnaire (SHEQ) was developed to measure adolescent perceptions of mental and physical health self-efficacy. A revised version of the SHEQ was administered to 449 high school students in grades 10-12. Twelve school nurses were asked to rate the items on the SHEQ, indicating how competent they believed the average high school student to be in each behavior. Data analysis showed the SHEQ to have sturdy reliability and validity properties and to be a useful tool in evaluation studies addressing adolescent health issues. The results indicated that psychosocial health issues troubled the adolescent slightly more than did physical health issues. Findings suggest that teenagers are fairly consistent about their self-beliefs. Mental health problems were concentrated on anxiety-producing events and physical health difficulties centered around daily routines. Managing sources of anxiety and managing daily, routine behaviors were perceived by the students to be relatively difficult. Gender differences appeared throughout the analyses. (NB)