In a search for mutations of the TP53 tumour suppressor gene in lung cancer samples from gold miners in the Witwatersrand, South Africa, using heteroduplex and single strand conformation polymorphism (SSCP) analysis, a nonsense mutation was found in exon 6, consisting of a C to T transition and resulting in chain termination of the TP53 gene. The mutation occurred in a small cell lung cancer sample and is the first reported codon 196 TP53 mutation in both radon-associated and small cell lung cancer (SCLC) material.