Our experience with 294 regional lymph node dissections in 250 patients are reviewed. The relationship between the Clark's level of invasion and the thickness of the primary is related to regional lymph node metastases. Patients with Clark's Level III melanoma had a 29% incidence of regional lymph node metastases, Clark's Level IV had a 42% incidence of regional lymph node metastases and Clark's Level V a 58% incidence of regional lymph node metastases. Primary melanomas greater than 1.5 mm in thickness had a 38% incidence of positive regional lymph nodes. We therefore recommend a regional lymphadenectomy in patients with Clark's Levels III, IV and V and all melanomas that are greater than 1.5 mm in thickness. A new technique is described which is helpful in localizing the direction of ambiguous lymphatic drainage in patients with truncal melanoma. The use of radioactive colloidal gold scanning has been useful in predicting lymphatic shed in these ambiguous truncal melanomas. Certain technical aspects of inguinal lymph node dissection are emphasized in an attempt to reduce the morbidity of these dissections. It is emphasized that iliac-obturator lymph node dissections are not performed unless the inguinal lymph nodes are found to be involved by frozen section examination at the time of surgery.