To evaluate the significance of positive surgical margins after vertical hemilaryngectomy for squamous cell carcinoma of the larynx. A retrospective review of patients undergoing hemilaryngectomy over a 20-year period. A major academic medical center. Fifty-six consecutive patients who underwent hemilaryngectomy between 1970 and 1990. Seventeen patients were excluded because of insufficient data or because they received postoperative radiation therapy. Eleven (28%) of 39 patients had cancer involvement of at least one margin. Two (8%) of 28 patients with negative margins and six (55%) of 11 patients with positive margins had recurrence. This difference in tumor recurrence is statistically significant. The mean disease-free interval prior to recurrence was 25 months, with no significant difference between the two groups. The mean follow-up periods for patients with positive vs negative margins were not statistically significant. There were no significant differences in survival estimates between patients with positive margins and those with negative margins. Despite a sevenfold increase in tumor recurrence rates for patients with positive margins after hemilaryngectomy, there was no adverse effect on overall survival when these patients were managed with close follow-up and salvage surgery with or without postoperative radiation therapy for tumor recurrence.