The development of a micropyrolysis gas chromatographic technique for the determination of free choline in plasma and erythrocytes is reported as a means to clinically assess choline status. A micropyrolyzer syringe unit was fabricated and the method was standardized through repeated trials with a single plasma specimen. The interassay coefficient of variance was 1. 3% for the standardized trials on plasma and erythrocytes. Choline status was assessed in control women, mothers and premature infants at birth and up to 14 days of life. At birth, plasma choline levels in the infants (32. 2 +/- 5. 5 mumol/l) were significantly higher than those in the mothers (12. 9 +/- 2. 6 mumol/l) and the control women (16 VSports手机版. 9 +/- 1. 6 mumol/l). The infant's plasma choline concentrations had decreased significantly by 7 days of life and remained at the lower level at day 14, independent of the nutritional intervention administered. .