A total of 195 non-small cell lung carcinoma (NSCLC) specimens were studied for the presence of mutations in their ras family genes, for tumor vascularity, and for their immunostaining pattern with an antibody to vascular endothelial growth factor (VEGF). ras mutation was found in 37 of 104 (34.6%) adenocarcinoma specimens, in 0 of 64 squamous cell carcinomas, and in 2 of 27 (7.4%) large cell undifferentiated carcinomas.