A series of 54 resected primary non-small-cell lung carcinomas was analyzed for p53 gene mutations and for p53 protein accumulation and the findings were correlated with clinical parameters. Mutations in exons 5 through 8 of the p53 gene were identified by a denaturing gradient gel electrophoresis (DGGE) assay and cycle sequencing, whereas p53 protein accumulation was detected in paraffin-embedded tissue by immunostaining using 2 different murine monoclonal antibodies (MAbs) (BP53-12 and DO7). A p53 gene mutation and/or p53 protein accumulation was found in 37 of 54 tumors. Mis-sense mutations were closely associated with positive immunostaining, which was intense in 15 out of 17 cases with a mutation. In 10 tumors, obvious p53 accumulation was detected in the absence of mutations in exons 5 through 8. Conversely, only one of 8 p53 non-sense mutations led to detectable p53 accumulation. The most frequent single base changes were G --> T transversions and C --> T transitions. The presence of a p53 alteration was not related to age, tumor size, stage or histology. However, we found a significant inverse correlation between p53 alterations and the presence of a K-ras mutation. This was reflected in the overall postoperative survival data: patients with p53 alterations in their tumors tended to have a better prognosis than those without a p53 alteration; however, this difference was lost when cases with a K-ras mutation were omitted from the analysis.