Changes in intestinal microbial flora are reflected in the faecal concentrations and production rates of short chain fatty acids. However, since no data on the latter are available in neonates, the aim of this study is to provide information on short chain fatty acids in faeces from normal neonates. Faecal samples were collected immediately after birth (meconium) and on the 4th day of life in 13 healthy, full-term neonates. The production capacity was evaluated by a faecal incubation system. Concentrations of short chain fatty acids were low in meconium (11.2 + 3.9 mmol/l (mean +/- SD], equivalent to about 10% of the adult level (p less than 0.01), but increased significantly during the first 4 days of life to 28.4 +/- 20.1 mmol/l (p less than 0.05). The fermentation pattern (i.e. relative composition of different acids) showed differences between adults and neonates, primarily due to a higher proportion of acetate found in the latter. The ratio acetate/propionate/butyrate/other acids was 89/5/5/1 in 4-day-old neonates compared to 65/18/11/6 in adults (p less than 0.001). Our findings correlate well with the postnatal microbial colonization of neonatal colon.