Trichinella spiralis occupies an intramulticellular niche in the small intestinal epithelium, and thus we examined the intestine and gut-associated tissues for proinflammatory cytokines during the infection. We document the patterns of interleukin-1 (IL-1), IL-6, gamma interferon, and tumor necrosis factor alpha mRNA expression in the duodenum, jejunum, Peyer's patches, mesenteric lymph node, spleen, and liver in T. spiralis-infected rats. By reverse transcription-PCR detection of mRNAs, IL-1beta was found increased in the jejunum but only on day 2. The jejunal IL-1beta increase was attributed to the epithelium by isolating epithelial cells and then depleting them of intraepithelial lymphocytes prior to analysis. The only cytokine for which mRNA was substantially increased in tissues later in infection was tumor necrosis factor alpha in the spleen and, to a lesser extent, in the mesenteric lymph node. In fact mRNA levels for some cytokines declined below uninfected levels in some organs during the infection. IL-1 may be important in the initiation of the intestinal inflammatory response to this infection.