This study was designed to test whether the Oregon THINK FIRST-Head and Spinal Cord Injury Prevention Program, developed for the high school audience and previously shown to have a beneficial effect, would have the same effect on students in middle school. During the spring of 1989, four schools (two high schools and two middle schools) participated. Two weeks before and after the presentation of the THINK FIRST program, 830 student questionnaires were distributed in classrooms. Questionnaire items were designed to measure knowledge, attitude, behavior, and demographic features. There was a significant difference between high school and middle school students on pretest knowledge (P = 0.0001). The average knowledge increase among all students was 0.81 correct responses (95% confidence interval: +/- 0.22) among 15 questions. The increment in knowledge did not differ significantly (P = 0.37) between high school and middle school students. One-way analysis of variance revealed no significant differences in pretest knowledge or knowledge increase associated with membership in Students Against Drunk Driving or acquaintance with someone having sustained a head or spinal cord injury. After the program, students were more likely to believe that there were actions they could take to keep from getting injured (P less than 0.0001). However, there was no change in self-reported seat belt use and most students reported that they "never" wore a bike helmet. The findings suggest that the THINK FIRST program is appropriate and beneficial for viewing by middle school-aged students.