Mohs surgery for basal cell carcinoma (BCC) of the skin attempts to ensure complete tumour removal by histological examination of the entire excision margin and further excision of involved sites. Advocates recommend its use in recurrent or incompletely excised tumours, poorly defined, histologically aggressive or large primary tumours and BCCs situated at high risk or cosmetically important sites. The claimed advantages over other surgical therapies are that it provides a better chance of cure and since less normal tissue is removed the simpler surgical repair ensures a superior cosmetic result. This review examines the published evidence that supports the enthusiasm for the use of Mohs surgery in the treatment of BCC, contrasting cure rates and cosmetic outcome with results achieved by attempted single complete excision and examines the 2 principles upon which Mohs surgery is based, namely that BCCs spread by contiguous growth and that all tumour cells have to be destroyed to achieve a cure.