AbstractThis clinicopathologic study was undertaken to determine the meaning of surgical margins “involved” with carcinoma. The fate of hemilaryngectomy patients whose specimens had this finding was compared with that of patients who had “uninvolved” margins.A consecutive series of 111 hemilaryngectomies performed for previously untreated invasive epidermoid carcinoma was analyzed. Serial step sections in a longitudinal plane were available for re‐examination and re‐evaluation of the surgical margins in each case. Clinical follow‐up on every patient was current through 1972.Thirty‐nine patients had cancer involvement of a margin in the hemilaryngectomy specimen. None of these patients received any immediate therapy but were followed only. Seven of these patients (18 percent) subsequently developed a biopsy proven local recurrence. Four of the 72 patients (6 percent) with uninvolved margins developed a local recurrence. The site of the positive margin in the specimen was compared with the clinical site of recurrence.The seven local recurrences in patients with positive margins were treated with full course irradiation or total laryngectomy. All of these patients are alive and free of cancer or have died of other causes without evidence of cancer. Of the four local recurrences in patients with negative margins one died of cancer; two are living and well, and one died of other causes.This study provides evidence to support the conservative management of those hemilaryngectomy patients who have involved margins in the resection specimen. No immediate treatment is required. Careful follow‐up is indicated with 18 percent chance of clinical recurrence. These biopsy proven recurrences can then be successfully treated with total laryngectomy or full course irradiation.Utilizing this approach none of the 39 patients with involved margins died of cancer in the 5 to 12‐ye