A patient with the naevoid basal cell carcinoma syndrome developed a secondary carcinomatous deposit in the pelvis. Persisting tumour in the skull and the secondary deposit in the pelvis contained areas of squamous differentiation. This confirms that the appearances of baso-squamous (or transitional or metatypical-cell) carcinoma can develop from typical basal cell carcinoma which had not been subjected to radiotherapy or to more than one surgical excision.