A survey of the birth prevalence of congenital anomalies among newborn infants in Japan is under way at a large maternity hospital in Tokyo. Of 14,430 consecutive newborn babies (7,455 M; 6,975 F), 33 had a multiple congenital anomalies (MCA) syndrome. These included 2 with trisomy 13 (including a mosaic), 3 with trisomy 18 (including 1 mosaic), 16 with trisomy 21 (including 1 mosaic), 1 with cri-du-chat syndrome, 1 with 5p partial trisomy, 1 with Hallermann-Streiff syndrome, 1 with Treacher-Collins syndrome, 1 with achodroplasia, 2 with arthrogryposis multiplex congenita, 1 with hemihypertrophy, 1 with Wiedemann-Beckwith syndrome, 1 with asplenia syndrome, 1 with Klippel-Trenaunay-Weber syndrome, and 1 with probable Marfan's syndrome. Except for one infant with Ullrich-Turner syndrome, cases with sex-chromosome aberrations could not be diagnosed neonatally on a clinical basis.