A purified flagellar pocket fraction of the Trypanosoma brucei AnTat 1.1E clone was used for the generation of polyclonal antiserum in rats. Anti-flagellar pocket antibodies present in this serum recognized several proteins distinct from the major variant surface glycoprotein (VSG). In Balb/c mice, flagellar pocket immunization resulted in partial resistance towards the challenge with a low dose of parasites. This was accompanied by the induction of specific IgG2a antibodies. In an attempt to discover protective parasite antigens, antiflagellar pocket serum was used for the screening of a T. brucei bloodstream form cDNA library constructed in the lambdagt11 bacteriophage expression system. Through antibody panning and VSG elimination, 15 specific cDNA inserts were selected. Most intriguing was the observation that in addition to two clones encoding the invariant surface glycoprotein 75 (ISG75), 10 out of 15 independently selected cDNA inserts encoded the trypanosome heat shock protein 60 (tHSP60).