The prognostic role of cell kinetics (expressed as 3H-thymidine labelling index, 3H-TdR LI) was assessed on 145 patients with pathologic stage II melanoma subjected only to therapeutic lymph node dissection. The 3H-TdR LI determined on metastatic nodes was related to relapse-free survival and to survival. In particular, 3-year relapse-free survival was significantly different from patients with slowly and rapidly proliferating melanomas (40% vs 22%, P = 0.007), and this finding was consistently found for overall survival (68% vs 46%, P = 0.007). Moreover, in patients with high 3H-TdR LI tumours, the risk of relapse and death within the first year from lymphadenectomy was two-fold that of patients with low 3H-TdR LI tumours. Multiple regression analysis showed that 3H-TdR LI retained its prognostic significance on relapse-free and on overall survival even when the number of involved nodes and type of nodal metastases were considered. Present findings suggest that 3H-TdR LI can contribute to select high-risk stage II melanoma patients.