Objective:To analyse and quantify the omission errors linked to physicians' prescribing and errors linked to nurses' transcription and to identify the type and frequency of factors associated. No pharmacological factors are taken into account.Design: Analysis of physicians' prescriptions and nurses' transcriptions in chemotherapeutic treatments (20 patient files) and nonchemotherapeutic treatments (20 patient files) retrospective study.Setting:Paediatric oncohaematology unit.Main outcome measures :categorisation of physicians' prescriptions as complete or incomplete, categorisation of the various nurses' transcriptions as correct or incorrect. Results: Physicians' prescriptions were complete for 61.6% of nonchemotherapy treatments. As each prescription is transcribed twice, two nurses' transcription sheets are filled in by the nurses. At the first transcription 79.3% of nonchemotherapy prescriptions and 88.2% of chemotherapy prescriptions were transcribed correctly, while in the second sheet these percentages were respectively 96.2% and 93.7%. Conclusions: Too many sheets of paper generate confusion and increase the risk of errors. The several transcriptions are, in both types of treatment, sources of errors. The problems identified in this study allowed us to open a discussion as how to improve the physicians prescriptions and the nurses' transcription sheets.