SummaryExtraction ofLeptospira interrogans(serotype,bifexa)with 0·2% trypsin yielded three precipitating antigens (‘axial filament’; antigen ‘d’; antigen ‘e’) as detected by immunodiffusion against rabbit antileptospiral serum.In contrast to ‘axial filament’ antigen, antigens ‘d’ and ‘e’ could be detected only in stationary phase leptospires. Protein antigen ‘d’ was purified and gave rise to monoprecipitin sera in rabbits. Monoprecipitin sera against both antigen ‘d’ and ‘e’ were also produced by immunizing rabbits with specific immune, precipitates in agar.Rabbit anti‐‘d’ and anti‐’ e’ immunoglobulins were initially of the 19S type but subsequently became solely 7S.