Mohs' surgery for basal cell carcinoma (BCC) is widely recommended by dermatologists as first line surgical therapy for recurrent or ill-defined skin tumours. The technique assumes that BCC spread by contiguous growth and that all tumour cells have to be removed. Advocates claim that Mohs' surgery provides a better chance of cure, and because less uninvolved tissue is excised the smaller defect can be readily closed resulting in a superior cosmetic result. This review examines the evidence for these claims.