The People's League of Health (England) appointed a special committee in July 1935 to study the influence of the nutrition of expectant and nursing mothers on maternal and infant mortality and morbidity. The primary investigation was conducted from March 1938 to t he end of 1929 and was planned to reveal whether additions of vitamins and minerals to the food would be beneficial to the course of pregnancy and labor and to the newborn infant. 5022 pregnant women participated in the investigation. These women were patients at the antenatal clinic s of participating hospitals from the initiation of the study, exclusive of those women whose pregnancy was beyond the 24th week and those suffering from any physical disease or abnormality. The women were divided into experimental and control groups with the experimental group receiving the vitamin supplements. Within each of these groups women we re classified into women pregnant for the 1st time and women with a history of 1 or more pregnancies as well as a division of women under 25, women between 25 and 30 years, and women who were older than 30. It was found that for all ages the percentage of toxemia in the treated primiparae is significantly lower than among the controls, 27.1% in contrast to 31.7%. For sepsis there is no satisfactory evidence that supports treatment with vitamin supplements. A smaller incidence of prematurity was revealed among the treated women, and this is particularly significant since about 50% of infant deaths under 1 month are due to prematurity. Although the percentage of children breast-fed increased with extended treatment, it is only when the mother had taken the supplementary diet for 24 weeks and over that their ability to breast-feed was slightly better than that of the controls. It might be expected that as the infants of the treated mothers had the more positiv e experience in regard to prematurity and birth weight they would show lower rates of stillbirth and neonatal mortality. This was found to be the case in regard to stillbirth but not in regard to neonatal mortality which is notably higher in infants born to treated primiparae and slightly higher in treated multiparae.