We evaluated the accuracy of primary health care providers' predictions of parents' adherence to their children's short-term antibiotic regimen and a scheduled follow-up appointment. Adherence predictions were compared with objective measures of the parents' adherence. Providers were poor predictors of non-adherence, greatly overestimating the percentage of parents who would be adherent. Non-adherence is typically addressed by applying adherence improvement strategies to all patients. Recent pediatric research, however, suggests that applying contingency-based interventions for adherent patients can result in later non-adherence if the strategies are withdrawn. Inaccurate predictions of adherence will result in many non-adherent patients not receiving a needed intervention. The results indicate the need for strong behavioral predictors that result in more accurate identification of patient non-adherence to guide further applications of adherence improvement strategies.