Background As school-based health centers (SBHCs) continue to grow, it remains important to study use of the centers. The extent to which mental health problems exist in the students with access to the centers, whether those students are using the available services, if they are satisfied with the services, and the reasons for nonuse by those students who do not enroll are all meaningful questions. Methods The above issues were studied in an urban high school with a 2-year-old SBHC by administering questions during physical education classes on health center use and mental health concerns. The 630 respondents were 45% male, 55% female, 61% black, 29% Hispanic, 54% in grades 9 or 10, 46% in grades 11 or 12. Results Sixty percent of the students were registered in the SBHC; 40% were not registered. Seventy-five percent of registered students reported average use (≤3 visits); females were more likely than males ( P =.017) to be frequent (>3 visits) users of SBHC services. Mental health problems among all participants included depression in 31%, use of alcohol 1 time or more per month in 21%, use of alcohol daily in 5%, suicidal ideation in 16%, history of a suicide attempt in 10%, knowing someone who had been murdered in 50%, and being in at least 1 fight at school in 26%. Frequent users, average users, and nonusers did not differ by age, grade, race, or any of the measured mental health problems. Among the 472 students who completed the survey section on SBHC perceptions, 305 described health center use: 92% were satisfied with health center services, 79% were comfortable being seen in the SBHC, 74% believed visits were kept confidential, 61% told their parents about each visit, and 51% considered the SBHC their regular health care source. The health center was used for mental health services by 34% and sexuality-related care by 15%. The 167 students who described reasons for not using the SBHC most frequently reported that they already had a physician (60%), did not need it (50%), prefer continuing previous health care (45%), did not get around to it (30%), parents were opposed (20%), were not comfortable (19%), did not know about the service (19%), and did not want problems known (19%). Conclusions We conclude that, in this urban high school, (1) average users, frequent users, and nonusers did not differ in the mental health problems measured in this study; (2) those who used the SBHC indicated strong satisfaction with the care received; and (3) those who did not use the SBHC chose to stay away for a variety of reasons, most commonly the availability of other care or the perception of lack of need.