Antisera from guinea pigs made resistant to infestation with an ixodid tick of east and central Africa, Rhipicephalus appendiculatus, were used to identify the tick antigens they recognized by immunoblotting. Most of the antigens were found in tick salivary glands and in tick attachment cement. Antisera from R. appendiculatus-resistant guinea pigs also recognized some salivary-gland antigens in ticks of other species (R. pulchellus, R. evertsi, Amblyomma variegatum and A. gemma). Antibodies against the most strongly recognized R. appendiculatus antigen, a 20-kDa molecule, were only poorly reactive with similar-sized molecules in the other ticks. A 94-kDa antigen, which appeared to have broader cross-reactivity, was purified from R. appendiculatus attachment cement, and a monospecific rabbit serum was raised against it. This antiserum clearly recognized a molecule of similar molecular weight in R. pulchellus and R. evertsi. Intravenous inoculation of rabbits with the purified molecule elicited delayed-type hypersensitivity to the antigen. The hypersensitive rabbits demonstrated resistance to feeding of R. appendiculatus ticks but slight enhanced feeding of R. pulchellus ticks. These results are discussed with respect to their relevance for artificial induction of tick-feeding resistance.