In contrast with neonatal intensive care services, paediatric intensive care units are relatively new; thus, it is not surprising that their clientele has not been well described in the medical literature. In order to better define it, we did a retrospective analysis of 4646 consecutive admissions of children aged between a week and 18 years to a multidisciplinary paediatric intensive care unit over a period of five years (1979-83). This unit belongs to a 700-bed paediatric hospital delivering medical as well as surgical tertiary care. Of the 4646 admissions, 2527 (54.3 per cent) were surgical and 2119 (45.6 per cent) medical. There were multiple diagnoses on admission. Among the most frequent diagnoses were major trauma (9.6 per cent of total), intoxications (4.6 per cent) and congenital cardiopathies in the postoperative phase of a corrective or palliative surgery (tetralogy of Fallot (2.8 per cent), ASD (2.7 per cent), etc.) The global mortality rate was 5.8 per cent (268/4646). Severe infections and cardiopathies, mostly congenital, were responsible for almost half the deaths (24.2 per cent each). This description of patients and problems encountered in a paediatric intensive care unit should facilitate planning for personnel training and can be used to establish guidelines for reducing mortality.