Cytogenetic investigation of nine pancreatic carcinomas revealed structural rearrangements of chromosome 19 in eight cases, resulting in a high frequency of 19p losses and 19q gains. To characterize these imbalances further, we performed fluorescence in situ hybridization (FISH) analysis with 12 mapped and evenly distributed cosmids. The FISH study not only verified the cytogenetic findings but also disclosed additional chromosome 19 aberrations not detected by chromosome banding analysis. Seven carcinomas displayed 19p losses, always including 19p13.3, either through partial- or whole-arm deletions. Six cases showed gain of 19q, usually as one to two copies above the ploidy level. In one case, a high level of amplification in 19q13.1 was seen. The commonly overrepresented segment was 19q13.1-13.2. These results suggest that genes of importance in the development of pancreatic carcinomas are located in 19p13.3 and 19q13.1-13.2.