Accumulating evidence suggests that the p53 gene is a good target for molecular epidemiological studies to search for risk factors in carcinogenic events. The lung cancer incidence for females in Hong Kong is unusually high, ranking among the highest in the world despite a low percentage with a history of smoking. To gain insights into possible etiological risk factors responsible for this high incidence, we examined p53 mutations in 35 lung cancer specimens from Chinese females living in Hong Kong and compared them with 35 matched cases from Japanese women as well as previously reported p53 mutations in the world literature. p53 mutations in exons 5-8 were present in 20 and 31% of the Hong Kong and Japanese cases, respectively. Notably, single-base deletions within runs of identical bases were observed in 3 (43%) of the 7 mutations in the Hong Kong cases, in contrast to the absence of such mutations in the controls and the extreme scarcity in the literature, suggesting that distinct environmental and/or genetic factor(s) might be involved. Although the frequent occurrence of characteristic single-base deletions could be a reflection of mutator mutations leading to inefficient mismatch repair of slipped strand mispairings, none of the lung cancer specimens exhibited such microsatellite instabilities.