Aberrations of the p53 gene in 27 solar keratoses were examined by the polymerase chain reaction and single-strand conformation polymorphism and DNA sequencing analyses. In a series of Japanese patients, eight of 27 cases (30%) of solar keratosis showed structural abnormalities of the p53 gene. Six of eight aberrations of p53 gene were determined to be single nucleotide substitutions, and five of these were located at a dipyrimidine site. In solar keratosis, noticeable mutations were C to T in three cases, and one each of C to A and T to C nucleotide changes. p53 protein was detected immunohistochemically in the nuclei of six of 27 cases (22%) of solar keratosis. Nuclear staining for p53 protein was only significantly correlated with the presence of missense mutation of p53 gene (p < 0.01). Aberrations of the p53 gene in solar keratosis may be a marker to predict early cancerous lesions.