From August 1980 to March 1981, paired cord venous blood and maternal antecubital venous blood were measured for triglyceride concentrations with the enzymatic method of triglyceride G-3-PDH UV end point assay, using the Hitachi Model 716 autoanalyser. The mean value of cord serum triglyceride concentrations in the cohort of 100 normal newborns was 28 ng/100 ml and the cut-off point of P95 was 48 mg/100 ml. In normotriglyceridemic newborns and hypertriglyceridemic newborns the mean values were 29 mg/100 ml and 66 mg/100 ml, respectively. However, the mean values of the corresponding triglyceride concentrations of maternal blood were not remarkably different among these 3 groups; they ranged from 190 to 193 mg/100 ml. The cord blood triglyceride level was much lower than that of maternal blood levels, with a ratio of 15% in the cohort of normal population of newborns and mothers. These findings showed that the cord serum triglyceride level was independent of the maternal serum triglyceride concentration and was of fetal origin. The relative impermeability of the placenta to this serum constituent and the lack of utilization of fat as a major source of energy in the period of normal intrauterine fetal life may, in part, account for the low serum triglyceride level in cord blood.