Controlled trials have shown treatment to be successful in reducing stuttering and enhancing fluency in the short-term for most children and adolescents. Regrettably up to 30% have been found to experience significant loss of fluency after 12 months. While this rate of relapse occurs in a significant minority, research should be investigating determinants of this process. However, research into relapse following treatment for stuttering in children has been scarce. To date, anecdotal material predominates. Another problem with this research lies in the difficulty in objectively defining relapse. In order to enhance our understanding of the relapse process, the present study’s purpose was to investigate predictors of relapse in older children. Subjects included 77 children and adolescents aged 9–14 years who were diagnosed as having stuttered for at least 1 year. All successfully participated in treatment and were assessed 12 months later. Possible determinants investigated consisted of pre- and post-treatment factors, including demographic variables, severity of stuttering, and anxiety levels. A standard regression analysis was performed to isolate factors that predicted the likelihood of relapse. Only pre-treatment stuttering frequency measured by percentage syllables stuttered and trait anxiety post-treatment significantly predicted stuttering frequency 1-year post-treatment. Those having a severe stutter before treatment and those who were less anxious immediately post-therapy were those susceptible to higher levels of stuttering in the long-term. Although frequency of stuttering is not an exhaustive measure of relapse, the present study offers an elementary ability to predict those children at risk of relapse following successful treatment.