Abstract
Preliminary differentiation of Leptospira interrogans serovars hardjo and balcanica can be made with antisera that are collected from hamsters after experimental infection with serovar hardjo and selected for high homologous and low or nil heterologous titres, as measured by the microscopic agglutination test. Rabbit antisera against serovars hardjo and balcanica, cattle antisera against hardjo and sheep antisera against the serogroup Hebdomadis each agglutinated hardjo and balcanica to a similar titre.