Abstract
A case of opocephaly in inbred guinea-pig strain 2/N and another in strain 13/N, a conjoined twin and an opocephaly concurrent with conjoined twins in the Dunkin-Hartley/FD strain are described. The incidence of congenital malformations in the inbred strain 2/N and strain 13/N was 0·0013 and 0·0073% respectively. The incidence in the random-bred Dunkin-Hartley/FD strain was 0·0007%.