the risk factors related with the gastroduodenal peptic ulcer were compared in a sample of 76 workers divided in two groups: exposed and not to nigth shift work as well as among the subgrups of the first one. the study design was analytic type of traverse court with a not probabilistic sampling. the test chi-square was applied (alfa>=95%) for the significance of the differences among the groups. the exposed group to night shift work and the subgrup with rotative quick changes shift work they presented bigger incidence of the risk factors for that desease. the night shift work and specifically the workers with rotative quick chances had more appropriated conditions for happening of the gastroduodenal peptic ulcer because the frequency of appearance of the risk factors and they presuppose bigger interaction with circadian rhythm dysruptions.