AIMS: To examine the adequacy of instructions to monitor for haematological adverse drug reactions in the Summary of Product Characteristics. METHODS: We searched the United Kingdom eMedicines Compendium to identify instructions to monitor for haematological adverse drug reactions, and selected 84 Summaries of Product Characteristics for nonhaematological drugs, which were then scored independently by five clinicians, using a scale we devised, the Systematic Instructions for Monitoring (SIM) score. A subset of comparable summaries from Australian and United States summaries was also examined. RESULTS: The SIM scores for the five clinicians agreed well: Kendall's coefficient of concordance = 0.937, P <0.0001. The median SIM score for the 84 UK summaries was 13 [95% confidence interval (CI) for median 12, 15] out of a possible 31. Over 40% fell below a hypothetical minimally acceptable score of 12/31. SIM scores were on average 2.0 (95% CI 0.4, 3.8) higher for Australian summaries; US summaries had intermediate scores that did not significantly differ from those in Australia or the UK. CONCLUSIONS: Instructions on monitoring for adverse drug reactions are often inadequate. Pharmaceutical companies and regulatory agencies should produce clear guidance on monitoring, and the data to support it.