Non-immune hydrops fetalis is becoming a relatively more important cause of hydrops as the incidence of rhesus-related hydrops falls. We describe a series of 33 cases, occurring over a 7 year period covering most of the 1980's. We found a very wide range of aetiological factors, but cardiac conditions, both structural and dysrhythmic, formed the largest subgroup (12 cases, 36%). Seven cases (22%) remained idiopathic. Prognosis was very poor, with only 4 infants surviving. Outcome was best in the cases due to intra-uterine supraventricular tachycardia. Nineteen cases were detected antenatally, but except in the cases of fetal tachyarrhythmias, this had little effect on outcome.