The aim of our work was to develop a fast, reliable and sensitive PCR method to detect K-ras mutations in various clinical samples. There is a need for an unimpeachable method for early diagnosis and/or screening of pancreatic cancer (PC). We optimized and subsequently analyzed four methods based on mutant-enriched PCR for the sensitivity, cost and time expense. Using the selected optimal method we examined codon 12 K- ras mutations in a study population of 59 patients with upper GIT malignancies. Reliability of the genotyping was confirmed by sequencing. By using the best of our modified mutant-enriched PCR methods we achieved sensitivity of 1:1 x 10(5). Further studies are necessary to determine the optimal biological material sampling in PC.