Microdialysis is a new method for continuous metabolic monitoring. We studied the possibility of using microdialysis in neonates treated in a paediatric intensive care unit after surgery. A microdialysis catheter was inserted in the abdominal subcutaneous adipose tissue in 14 neonates for a median of 93 h (range 24-106 h). In four neonates, two microdialysis catheters were used simultaneously. Samples were taken hourly for analysis of glucose, lactate and glycerol. Dialysate and blood concentrations were compared. Serum/whole blood glucose values (n = 68) were in the range 2.1-15.4 mM. The serum glucose levels showed good agreement with the dialysate concentrations of glucose, although these infants were subjected to various forms of stress, drugs and glucose infusions. The whole blood glucose levels were significantly lower than the dialysate levels. The microdialysis concentrations of glucose varied considerably. As almost identical dialysate glucose levels were found when two microdialysis catheters were used simultaneously, the variability probably reflects true changes in blood glucose levels. Our results indicate that microdialysis can be used in neonates.