The reverse transcription-polymerase chain reaction-single strand conformation polymorphism (RT-PCR-SSCP) analysis and sequencing were used to examine p53 gene alterations in 18 surgical specimens of primary lung cancers obtained in Japan. Somatic mutations resulting in amino acid changes were found in eight of the 18 cases (44%). Seven missense mutations were located in amino acid-conserved domains or their vicinities (codons 110 to 307). Most mutations were found at G-C pairs, suggesting that specific carcinogens are involved in the etiology of lung cancer. The p53 mutations showed a significant association with a history of smoking (P = 0.0294). We suggest that the p53 mutations may be associated with smoking-induced lung carcinogenesis.