This study deals with changes in pancreatic vessels in cases of chronic pancreatitis. In particular the hypothesis that the diameter of the arterial vessels is reduced is examined statistically. Histological preparations from two groups, stained by the Elastica van Gieson method, were used for the investigation: Group I consisted of 50 section cases with healthy pancreatic tissue, group II consisted of 50 operative cases of chronic pancreatitis. At a 320-fold magnification, media thickness, vessel diameter, and intima thickness of four arterial vessels in each case were determined by a measuring scale in the ocular of a light microscope. The test results were transferred to perforated cards and analyzed statistically by computer. In the region of the endothel, the arterial vessels show cell nuclei projecting into the lumen. Especially remarkable is the thickening of the subendothelial intima tissue in the form of intimafibrosis and intimaelastosis. Atrophy of the media is noted in later stages, and it finally dissolves. The lumen of the arterial vessels seems to be considerably constricted as compared to that of the venous vessels. In attempting to prove vessel constriction, it was assumed that a certain media thickness corresponds to a certain vessel radius. Thus, we determined the relations between media thickness and vessel radius in both groups. Using regression lines as a model, we found vessel constriction to be statistically significant. However, although regression lines for the correlation between assumed vessel radius (sum of vessel radius and intima thickness) and media thickness are quite close, they are still significantly different. This remaining difference could have been caused by alteration in the media or also by additional influencial characteristics that differ in the two test groups. Therefore, the effect on the relationship between vessel radius and media thickness was examined with regard to the following variables: distribution of age, sex, and phases of parenchym reduction. Results show that the differences between the two groups were hardly influenced by age. The different distribution of sex seems to weaken the result more than to intensify it. Finally, the phase of parenchym reduction corresponds to the extent of vessel alteration. These vessel alterations probably represent an adaption of the reduced parenchym to the lowered demand for blood. On the other hand, it is rather unlikely that such alteration is an important pathogenetic factor of chronic pancreatitis or a consequence of exterior pressure caused by perifocal inflammation and incisive cicatricial tissue.