Patients in paediatric intensive care units (PICU) often receive numerous medications by the parenteral route. Frequently two or more drugs are delivered simultaneously through the same line and the risk of physicochemical incompatibilities is thus important. The objectives of this study were 1) to identify prospectively the combinations of injectable drugs administered in the PICU of our university hospital and 2) to analyze them according to information found in the literature. The data were collected by a pharmacist over a 30-day period and classified in three categories: compatible, incompatible and undocumented. Nineteen patients were included in the study with a median age of 3.2 years. The mean number (+/- SD) of injectable drugs per patient and per day was 6.5 (+/- 2.8), for a total of 26 drugs and 7 solutes. 64 combinations of drugs were observed with 2 (31.3%), 3 (45.3%), 4 (10.9%) or 5 (12.5%) drugs. 81 drug-drug and 94 drug-solute combinations were recorded. Among these, 151 (86.3%) were compatible, 6 (3.4%) incompatible and 18 (10.3%) undocumented. The incompatibilities included furosemide (Lasix), a drug in alkaline solution and Vamina-Glucose, a total parenteral nutrition solution. No clinical consequences resulting from drug incompatibilities were shown in this study. We suggest that in vitro compatibility tests on standard drug combinations, as well as a training program for nurses on drug incompatibility problems would sensitively increase the security of parenteral drug administration.