In order to assess children's perceived vulnerability to health problems, a longitudinal study was designed to observe third and seventh graders at five intervals over a 2-year period. The hypotheses tested concerned relationships between perceived vulnerability to health problems and age, sex, and socioeconomic status. Data were obtained from a group administered a 15-item questionnaire; a characteristic item illustrating the basic format of these questions was "What chance is there of your getting the flu during this next year?" The specific health problems investigated were a bad accident, a rash, a fever, having a tooth pulled, a sore throat, a toothache, a cold, bleeding gums, an upset stomach, being sick enough to miss a week of school, a cavity, a bad headache, breaking or cracking a tooth, and cutting a finger. Seven additional questions were used as filler items. For each question the subjects selected one response from seven alternatives in a quasi-interval scale. Results indicated that age was significantly but nonlinearly related to perceived vulnerability. Females showed significantly higher levels of perceived vulnerability than did males. In the younger sample, perceived vulnerability was related positively to higher socioeconomic status. Implications for theory and health education programs are discussed. (Author/DB)