Trichinellosis is a worldwide zoonosis caused by the parasitic nematodes belonging to the Trichinella genus. This chapter describes the different aspects of epidemiology of infection, the life cycle of the parasite and the host immune response to the different species of Trichinella in humans, as well as in rodents which represent the most studied experimental model. The roles of antibodies, T cells, mast cells, eosinophils and neutrophils in immune responses to this nematode are considered in experimental as well as in human infections. Immunopathological aspects of infection are also illustrated. Particular emphasis is given on the clinical diagnosis of trichinellosis which is difficult because of the lack of pathognomonic signs or symptoms. Therefore, anamnestic data are of great importance in diagnosing the infection. High eosinophilia and increased creatine phosphokinase (CPK) activity in the serum are the most frequently observed laboratory features, but only the finding of parasites in a muscle biopsy and the detection of specific circulating antibodies can confirm the diagnosis. The medical treatment includes anthelmintics (mebendazole or albendazole) and glucocorticosteroids. A section is devoted to control measures, including a possible vaccine for which several molecules are under investigation.