Between 1988 and 1995, 73 adolescent athletes treated with the Boston Overlap Brace for spondylolysis were reviewed to evaluate improvement in pain score and activity level. A favorable clinical outcome was achieved in 80%. Girls and boys who participated in high-risk sports were five times more likely to have an unfavorable clinical outcome than those who participated in low-risk sports (odds ratio = 5, 95% confidence interval = 2.4-7.5, P = .003). In addition, acute onset of pain and hamstring tightness were associated with a worse outcome. Athletes with symptomatic spondylolysis treated with an antilordotic brace can expect improvement in their clinical course and return to sports participation in 4-6 weeks.