Antisera raised in rabbits against two nontypable group B streptococci, which were not agglutinable in a specific group B antiserum, were tested with acid extracts of 78 nontypable human group B streptococci. One antiserum (12351) reacted with 15 strains, and the other (7271) reacted with only 2 strains. Antiserum to Wilkinson's strain SS 1169 (NT 1) reacted with three strains. Antiserum against strain 12351 appears to be a useful antiserum against a new type antigen, which is probably polysaccharide in nature.