We describe our initial clinical experience with the new hollow fibre membrane oxygenator Dideco Kids D100, used in five patients with a mean age of 21 +/- 28 days. The priming volume is 31 ml with a membrane surface area of 0.22 m2. Data were compared with those deriving from five patients treated with Dideco D901 Lilliput 1 oxygenator. Among patients treated by the new Dideco Kids D100 oxygenator, priming volume was significantly reduced and an easier blood gas delivery was evident.