PURPOSE: The aim of the present study was to evaluate the predictive value of volume of the specimen/body mass index (VS/BMI) ratio for recurrence after surgical therapy of pilonidal disease. METHODS: Ninety-eight patients with primary pilonidal disease were enrolled in this study. The VS/BMI ratio was calculated for each patient. This ratio was defined as the specimen index (SI). VS, BMI and SI were evaluated to determine whether there is a relationship between these parameters and recurrence of pilonidal disease. In addition, the predictive ability of SI for recurrence was analyzed by receiver operating characteristic (ROC) curve. RESULTS: VS and SI were found to be higher in patients with recurrence. ROC curve analysis showed that VS and SI are predictive factors for recurrence in patients treated with primary closure, nevertheless our new index had higher sensitivity and specificity than VS (sensitivity 85.7% vs 71.4% and specificity 90.7% vs 85.1%, respectively). The cut-off level for the greatest sensitivity and specificity for SI was 1.29. CONCLUSION: Recurrence is higher in patients with high VS regardless of the operation method. SI may be a predictive value in patients treated with primary closure.