Ulceration has been shown to be an adverse prognostic factor in primary cutaneous melanoma. However, the extent of ulceration required for histologic identification and biologic significance is unclear. We examined the impact of extent of ulceration on melanoma outcome in a cohort of 235 melanoma patients by evaluating the relationship between percentage of ulceration in the vertical growth phase of the primary tumor and 2 outcome parameters: sentinel lymph node status and overall survival. We measured the diameter of the ulcerated area in millimeters over the diameter of the entire vertical growth phase. There was a statistically significant relationship between increasing percentage of tumor ulceration and both sentinel lymph node status as well as overall survival, with a binary cut-off point of 2% for sentinel lymph node status and 5% for overall survival. The percentage of ulceration provides additional prognostic information in predicting sentinel lymph node status and in determining survival in melanoma patients. These results suggest that no more than minimal ulceration is required to have a prognostic impact on melanoma survival.