Amniotic fluid glucose, beta OH butyrate, glycerol, and lactate concentrations were measured in 75 samples collected in the third trimester of pregnancy from 50 diabetic patients, all but four of whom required insulin. Increases in maternal fasting plasma sugar were accompanied by corresponding increases in amniotic fluid glucose and on occasion increases in amniotic fluid beta OH butyrate. These data correspond to previous reports of placental glucose transfer and in addition, provide statistically significant evidence of placental betaOH butyrate transfer since the hyperglycemic, hyperinsulinemic fetus of a diabetic mother would be a poor primary source for ketogenesis. Relatively poor correlation of elevated fluid levels of these solutes to fetal outcome probably reflects a low incidence of maternal hyperglycemia, ketogenesis. Relatively poor correlation of elevated fluid levels of these solutes to fetal outcome probably reflects a low incidence of maternal hyperglycemia, ketoacidosis, and over-all reduced neonatal morbidity-mortality rates in this group of metabolically well-controlled, predominantly insulin-requiring diabetic patients managed in a regional high-risk perinatal center.