The prevalence of overweight and obesity is increasing and contributes to the burden of ill health in the community. The impact of obesity on health-related quality of life has been less well studied than how it affects physical morbidity and mortality. A survey of health-related quality of life using the 12-item Short Form (SF-12) of the Medical Outcomes Study Short Form-36 was mailed to patients attending a family medicine clinic. Multiple regression analyses were used to investigate the relationships between scores on the mental and physical components of the SF-12 and body mass index (BMI) while controlling for age, sex, and family income. Responses were received from 565 subjects (53%). The relationships among BMI and quality of life in the mental and physical domains were nonlinear. Quality of life scores were optimal when BMI was in the range of 20 to 25 kg per m2. The National Heart, Lung, and Blood Institute has published evidence-based clinical guidelines for the identification, evaluation, and treatment of overweight and obesity in adults. Subjects with BMI in the range 18.5 to 24.9 kg per m2 are classified as having normal weight. These observations suggest that achieving a weight in this range will maximize the patient's subjective sense of well-being.