Time to recurrence varies inversely with thickness in clinical stage 1 cutaneous melanoma. The thickness of a tumor has been identified as the principal prognostic factor in cutaneous malignant melanoma. However, time to recurrence has not conclusively been related to thickness. A retrospective study of 216 patients with a primary cutaneous malignant melanoma that recurred was conducted to clarify this relationship and investigate possible independent relationships between age at diagnosis and sex of patients to time to recurrence. The results of analysis of linear regression revealed an inverse linear relationship between thickness and time to recurrence (p less than 0.001). Patients more than 50 years of age at the time of diagnosis were shown to relapse sooner than those less than 50 years of age (p = 0.014). Sex was not a significant factor in predicting time to recurrence (p greater than 0.10). These results suggest that thickness of tumor provides an indication of time to recurrence in those patients destined to recur and stress the need for long term surveillance in patients with a history of malignant melanoma because of the possibility of late relapse even with thin lesions. 