In this study expression of claudins 1, 3, 4 and 5 were studied in 118 cases of gastric carcinoma and compared with proliferation, apoptosis and E-cadherin expression. Expression of all these claudins could be seen in gastric carcinoma, most prominently for claudin 4, and least expression was found for claudin 5. All claudins showed significantly more expression in gastric carcinomas of intestinal type. Their expression was significantly associated with each other. Expression of claudins 4 and 5 was associated with E-cadherin. Strong expression of claudin 5 was associated with higher cell proliferation and apoptosis. Claudin 3 expression had an association with a better prognosis of the patients, especially in the intestinal type. The results show that expression of claudins 1, 3, 4 and 5 is lower in diffuse-type gastric carcinomas. Possibly they play a role in determining the diffuse phenotype and loose cohesion of cells in diffuse type of gastric carcinoma in a similar manner as E-cadherin. The loss of their expression does not clearly associate with poorer prognosis of the patients, except for claudin 3, where strong expression was associated with a better outcome of the patients, a feature especially related to intestinal-type tumours.