Histologic and quantitative techniques were compared in an evaluation of the intensity of Pneumocystis carinii infection in common shrews (Sorex araneus) at Espoo, southern Finland, from September 1992 to May 1993. The histological scores were comparable to the results of the cyst count technique. The number of P. carinii cysts found in common shrews was low compared to those reported by others in clinically ill laboratory rats. The inflammatory changes detected in the lung sections had no significant relation to the presence of P. carinii infection.