The complement-fixation test has been in routine use in the First U. S. Army Medical Laboratory for the diagnosis of trichinosis. On occasion the bentonite-flocculation test has also been performed. Recently we have developed an agglutination procedure with latex (polystyrene) particles which promises to be as specific and sensitive, but less laborious, than either the complement-fixation1or the bentonite2test. The latex test is performed in small volumes in order to conserve reagents and test serum and, because of its simplicity, may be adapted for use in any laboratory. Results obtained in parallel tests with the complement-fixation and latex methods are presented in this report. Materials and Method Preparation of Trichinella Extract.— Trichinella (Trichina) extract is prepared by the method of Bozicevich.2It is carefully titrated with a number of serums from patients known to have trichinosis. Lack of nonspecific and anticomplementary activity is assessed by testing