Delayed reconstruction following Mohs' chemosurgery for skin cancers of the head and neck. The case records of 52 patients with 55 cutaneous neoplasms treated by Mohs' chemosurgery and subsequently reconstructed by plastic surgeons were reviewed to determine if delay between resection and reconstruction adversely affected the outcome of reconstruction. Reconstruction was performed from 5 to 61 days after Mohs' chemosurgery for 45 basal cell carcinomas and 10 other cutaneous neoplasms. There were no complications during the interval between resection and reconstruction. Following reconstruction, minor wound complications occurred in 6% of patients; there were no major complications. Microscopic examination of the re-excised wound revealed residual disease in 2 of 45 cases of basal cell carcinoma and 0 of 10 other cutaneous malignancies. Both patients with residual basal cell carcinomas (i.e., false-negative margins after Mohs' surgery) had presented to the Mohs' surgeon with recurrent tumors. During a follow-up period of 3 months to 3 years after complete resection, recurrent tumor developed in 2 of 45 cases of basal cell carcinoma and 3 of 8 cases of squamous cell carcinoma. Delayed reconstruction, usually 5 to 20 days after Mohs' chemosurgery, can be performed without significant morbidity. Re-excision of the Mohs' chemosurgical wound for pathologic examination can detect residual disease and may be especially indicated for large recurrent wounds. 