OBJECTIVE To determine the effectiveness of wide vs narrow excision margins in the treatment of primary cutaneous melanoma. METHODS We conducted a search of MEDLINE and the Cochrane Controlled Trials Register as well as a manual search of the reference lists of all relevant papers. No language or date restrictions were applied. METHODS Only prospective randomized trials were included. METHODS Two reviewers independently extracted the data from each study. Outcomes evaluated were local and locoregional recurrences and overall mortality. Data were analyzed using Cochrane Collaboration Review Manager software. RESULTS Five randomized trials comprising 3313 participants were retrieved and analyzed. Pooled data showed no statistically significant difference in overall mortality when comparing wide vs narrow excision margins (odds ratio, 0.98; 95% confidence interval, 0.72-1.22; and test for overall effect of P = .88). There was no statistically significant difference in the occurrence of locoregional recurrence between 2 groups of patients (odds ratio, 1.18; 95% confidence interval, 0.98-1.41; and test for overall effect not significant at P = .08). Although statistically significant heterogeneity was not detected among included trials, there was considerable clinical heterogeneity. CONCLUSIONS Although this meta-analysis did not show any statistically significant difference between patients treated with wide or narrow excision margins insofar as overall mortality and locoregional and local recurrences, current evidence is insufficient to address the optimal excision margins for all types of melanomas. Further research is required to establish the appropriate local treatment for different types of primary melanoma and subgroups of patients.