The first documented report of an outbreak of human trichinellosis caused by Trichinella spiralis in Italy is described. Two family groups were involved. The source was wild boar meat products. The principal clinical features were fever (60%), myalgia (50%), and diarrhea (40%). The most useful laboratory indicators were eosinophilia (100%), elevated levels of creatine phosphokinase (CPK) (90%) and other muscle enzymes, parasite-specific IgG titers (100%), and anti-newborn larvae antibodies (30%). The levels of these responses correlated with the number of infective muscle larvae ingested, which was influenced by the length of time the ingested meat was cured. The clinical and biological features observed during human infection with T. spiralis appear to have been different from those reported during two outbreaks due to T. britovi, which occurred in southern Italy. The main distinctions between the two types of infections were a longer duration of parasite-specific IgG, increased CPK levels, and a more severe intestinal symptomatology in T. spiralis-infected patients than in those infected with T. britovi.