Selective suppression of the total IgE antibody response has been achieved in rats by injection of rabbit anti-rat epsilon-chain antibodies. This IgE-specific suppression was maintained during the course of a natural infection by the nematode Trichinella spiralis. Depletion of the IgE antibody response resulted in a marked reduction of the number of eosinophils attracted to the T. spiralis larvae encysted in striated muscle. Blood eosinophilia following T. spiralis infection, although reaching normal peak levels, was abbreviated in IgE-suppressed animals. Moreover, IgE-depleted animals were more susceptible to the infection; they harbored two to three times more larvae encysted in their muscles than their control litter mates.