OBJECTIVE: Patients' perceptions of the value of their antiepileptic medications are important factors in assessing antiepileptic drug therapy. We developed and validated a scale to combine patient-reported efficacy, convenience and tolerability of antiepileptic pharmacotherapy into a single measure of overall usefulness. METHODS: Neurologists in two practices assigned patients a priori to either a "doing well" or "not doing well' group based upon clinical assessment of efficacy, tolerability and convenience of each patient's antiepileptic medication. Adult outpatients on antiepileptic medications completed a four-item self-administered questionnaire. Patients scored the overall usefulness, efficacy, tolerability and convenience of their antiepileptic pharmacotherapy on visual analogue scales ranging from 0 to 100. Fisher's exact test was used to determine systematic differences in demographic characteristics or neurologist's assessment of the two groups. Differences between groups in mean overall usefulness and component scores were assessed using the t-test. A multivariate model was used to assess weights of efficacy, tolerability and convenience on the overall usefulness score. RESULTS: Sixty patients completed the questionnaire. Sixty percent (60%) were classified as "doing well" and 24 (40%) as "not doing well" a priori on antiepileptic medication. Both groups had similar demographic characteristics. The "not doing well" group had significantly more problems with efficacy, tolerability and convenience than the "doing well" group (p <0.001). The mean overall usefulness score was higher for the "doing well" group (88) compared to the "not doing well" group (53) even after controlling for all demographic variables (p <0.0001). Similar results were observed for efficacy and tolerability scores. No individual domain (efficacy, tolerability, convenience) had a disproportionate influence on the overall usefulness score. CONCLUSIONS: This patient-reported usefulness scale for antiepileptic drug therapy has potential application in research and clinical settings to discriminate between patients whose antiepileptic pharmacotherapy is efficacious, tolerable and convenient and those whose antiepileptic pharmacotherapy is not.