1. The sera of 18 goats were investigated for the bilharzia complement fixation reaction, using as antigen alcoholic extract of the livers of snails (Planorbis exustus) infected with cercariae of S. spindale.
2. The sera of 5 out of 7 goats harbouring S. mattheei, and of 4 out of 4 goats exposed to alimentary infection with S. bovis yielded positive results, the range of complement fixation varying from 5 to 20 M.H.D.'s.
3. The sera of non-infected goats and of 3 goats exposed to infection with cercariae of S. mansoni from which these animals appear naturally immune, yielded negative reactions.
4. The complement fixation reaction with cercarial antigen (S. spindale) has now been applied to infestation with 3 human and 4 cattle schistosomes, and its group applicability to mammalian schistosomiasis may be regarded as proven.