Specific antibody response and histopathological changes in the small intestine were studied in mice genetically selected for high and low antibody production (HL and LL, respectively) after oral infection with 50 muscle larvae of Trichinella spiralis. Specific antibody response, measured during the first 20 days after infection in the passive cutaneous anaphylaxis assay and the immunofluorescence test was high in HL and low in LL mice. The response of macrophages, intestinal mast cells, globule leucocytes and eosinophils was examined in the jejunum. It was concluded that the differences in antibody levels and macrophage activity between HL and LL mice are in keeping with published evidence. The cellular reaction of intestinal mast cells and globule leucocytes was delayed in LL mice compared to HL mice. The eosinophil response in HL and LL mice was the same. Consequently, apart from differences in macrophage activity and antibody production, HL and LL mice differ also in intestinal mast cell and globule leucocyte response.