A total of 138 capsulated strains of streptococci were isolated from pigs with various infections, notably septicemia and bronchopneumonia. Biochemically all strains were similar, and 31 strains were serologically identical to the previously described groups R, S, and RS streptococci, provisionally designated Streptococcus suis types 1, 2, and 1/2 by Elliot. The remaining 107 strains could be divided into six new capsular serotypes of S. suis.

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.

The main part of strains of Streptococcus mutans isolated from the present Danish material of blood from patients with subacute endocarditis and from human teeth belonged to two of five serotypes established by Bratthall, viz. type c and type e. Two new types were established: type f and type g. Strain SL‐1 seems to constitute a distinct type. Strains of serotypes a and b have not been isolated in Denmark, and strains of serotypes d, g and SL have been isolated from teeth only. The registered differences in biochemical behaviour warrant a proposal of a subdivision into three biotypes.

Streptococcus suis was isolated from 11 (10 per cent) out of 107 cases of endocarditis in slaughter pigs from which bacteria of any kind were isolated. Seven of the isolates belonged to the capsular serotypes 1, 2 and 1/2. Four were non‐typable owing to lack of capsule. The organism isolated most often was Erysipelothrix rhusiopathiae, which was found in 68 (64 per cent) cases.

A total of 252 strains of group B streptococci were serotyped and examined for their ability to ferment lactose (lac+), to hydrolyze salicin (sal+), and to produce hyaluronidase (hy+). Of these strains, 67 had been isolated from bacteremia and meningitis in infants less than 2 months old. Eighty-one strains were isolated from bacteremia and meningitis in adults, and 104 strains were from various other infections. Type III was the most common in neonatal disease, especially if isolates from cases of bacteremia in infants less than 10 days of age were not included. Only 6% of the strains were lac+. Sal+/hy+ strains were never type III, but 91% of the strains belonging to the other serotypes were sal+/hy+. Results showed that 81% of the sal+/hystrains and 95% of the sal-/hy+ strains were type III, and sal-/hy+ strains were more than twice as frequent as sal+/hystrains in serious neonatal infections, in contrast to the other two disease groups, in which the opposite was found to be the case. These reactions may be used as additional markers in epidemiological studies.