Patients with Hodgkin's disease and nodal non-Hodgkin's lymphomas seem to have an excess risk for other cancers. A high incidence of other cancers has also been found in some series of patients with gastric MALT lymphomas. In a series of 136 patients with gastric MALT lymphomas the occurrence and features of other cancers have been described. In order to evaluate their occurrence statistically (excluding skin cancers) standard incidence ratios (SRI) have been calculated, using the incidence rates of a Cancer Registry in Spain as a reference. A Cox's multivariate proportional hazard model was fitted in order to evaluate the influence of age, sex, histological grade and treatment with chemotherapy or chemotherapy plus radiotherapy in the development of other non-skin cancers occurring after the diagnosis of MALT lymphoma. Other cancers were detected in 16 of the 136 patients (11.7%); the other cancer was detected prior to MALT gastric lymphoma in 6 patients (4.41%), concomitantly in 4 (2.9%) and after diagnosis of the lymphoma in 6 (4.41%). Other cancers occurred in 14.4% of the male and in 8.3% of the female patients; in 12% of the patients with low grade and in 11% of the patients with high grade lymphomas. Of the 6 cancers that occurred after diagnosis of the gastric lymphoma, 3 did in the 80 patients (3.7%) that had been treated with chemotherapy, 1 in the 3 cases (33%) treated with chemotherapy and radiotherapy and 2 in the 53 patients (3.7%) who had not received chemotherapy or radiotherapy. The most frequent other cancers were lymphoid neoplasms and gastric carcinoma. There was not an excess of other cancers in the whole cohort or in the sex or histological grade strata. There was an excess close to significance (SIR =2.59; 95% CI:0.98-6.88) in the patients under 50 years of age. In the Cox's analysis, age, sex, histological grade and treatment did not influence the occurrence of other cancers after the diagnosis of lymphoma. In conclusion, in patients with gastric MALT lymphoma other cancers also occur. An excess incidence was not demonstrated, although it may exist in patients under 50 years. Of special importance is the occurrence of gastric cancer that appears concomitantly or after gastric lymphoma.