The spread of primary gastric non-Hodgkin's lymphomas of the mucosa-associated lymphoid tissue (MALT) to the perigastric lymph nodes is a very important step concerning the prognosis of these tumours. In order to evaluate the parameters that influence the infiltration of the lymph nodes we retrospectively investigated 145 surgical specimens with gastric MALT lymphoma. The involved factors, i.e. depth of infiltration, degree of malignancy, and largest tumour diameters were strongly intercorrelated and partly showed significant correlations with the lymph node infiltration as well. Further statistical analysis by means of logistic regression revealed that depth of infiltration was the only parameter that remained significantly correlated with lymph node infiltration. Our data further support the notion that the depth of infiltration is a very important prognostic factor in MALT lymphomas. This could contribute to the explanation as to why the so-called early lymphomas with an infiltration limited to mucosa and submucosa have a much better prognosis than more advanced tumours. Our data thus support the thesis that gastric MALT lymphomas show clinicopathologic similarities with gastric carcinomas. We suggest that the depth of infiltration should be included in the pathological reports concerning primary gastric lymphomas of the MALT.