Detection of K-ras mutations may be useful in the evaluation of pancreatic cancer. The aim of this study was to assess, in a prospective design, the diagnostic utility of K-ras mutation analysis in 62 consecutive fine-needle aspirates of pancreatic masses, using two PCR-based techniques-standard and enriched-with detection limits of a mutant allele in the presence of 10(2) or 10(3) wild-type alleles, respectively. Cytology alone offered a diagnostic sensitivity of 75%. The enriched higher sensitivity detection technique, in combination with cytology, offered a diagnostic sensitivity of 91% without false positives. The molecular analysis would have contributed to diagnosis in an additional 14 cases of pancreatic cancer. The standard technique contributed to diagnosis in an additional 9 cases. These results strongly support the use of the enriched method of detecting K-ras mutations as a complement to cytology in the evaluation of pancreatic masses.