PIP: 1 approach to the prevention of tetanus neonatorum (a leading cause of infant death throughout the world) is improving the quality of prenatal, obstetric, and postnatal maternal and child health services. Another complementary approach is the active immunization of women before or during pregnancy with tetanus toxoid. Work in progress at the Matlab field station of the International Center for Diarrheal Disease Research in Bangladesh (ICDDR,B) provided a unique opportunity to study the effectiveness of certain aspects of these 2 strategies. In 1974, during a field trial of cholera toxoid vaccine, 2 injections of an aluminum phosphate tetanus-diphtheria toxoid were provided as a control to a randomly assigned group of nonpregnant women. Beginning in June 1978, a program of immunizing women during pregnancy with aluminum phosphate-absorbed tetanus toxoid was initiated in conjunction with the implementation of a village based maternal and child health and family planning program in half of the same Matlab surveillance area. Throughout the period of these 2 programs, the ICDDR,B maintained an independent, longitudinal, vital registration system, identifying all births and deaths in the study area. In this analysis, all live births registered in the Maternal and Child Health-Family Planning and comparison areas during the September 1, 1978 until December 31, 1979 period were identified. These records were linked with any deaths recorded within 28 days of birth. The acceptance of tetanus vaccination during the 1974 cholera vaccine trial, by the mothers of these live births, was ascertained from the 1974 vaccine registers. The acceptance of vaccination during the 1978-1979 program was obtained from the field registers. For infants whose mothers had received 2 tetanus injections 48-64 months prior to delivery, the neonatal mortality rate was 63.8/l000 live births compared with 78.3/1000 for infants whose mothers did not receive tetanus immunization. Immunization of women with 2 tetanus injections during pregnancy reduced neonatal mortality rates to 42.8/1000, a reduction of 35.5/1000. Mortality on days 4-14 was reduced by about 70%. 1 injection during pregnancy did not appear to provide protection against tetanus neonatorum.