c-Ki-ras-2 sequences were visualized in paraffin-embedded sections from normal fetal and adult human pancreases, a chemically induced transplantable human pancreas carcinoma (PT-1) and three carcinomas of pancreas by in situ hybridization technique. A biotinylated 1-kilobase-pair (kb) EcoRI fragment of pHiHi3 DNA was used as probe and the oncogene was visualized as one or two large grains of reaction products produced by streptavidin-peroxidase complex and diaminobenzidine tetrachloride in more than 9% of normal pancreas nuclei. Its amplification in the chemically induced cell line was detected as one or more large grains in 72% of the nuclei and numerous cytoplasmic grains. The detection of oncogene in normal pancreases and its amplification in PT-1 cells was validated by Southern analysis of EcoRI digests of genomic DNA extracted from normal pancreases and PT-1 cell line. The oncogene was also demonstrated to be equally amplified in two adenocarcinomas and one undifferentiated carcinoma of human pancreas by in situ hybridization.