BACKGROUND: Iron deficiency anaemia (IDA) remains the most common cause of anaemia and is frequently secondary to occult gastrointestinal blood loss requiring further investigation. The study was designed to prospectively assess the adequacy of investigation of IDA and to establish whether a simple computerised prompt would increase the completeness of investigation of patients presenting to their general practitioners. PATIENTS AND METHODS: All men aged >20 and women aged >50 newly found to have a probable IDA (n=431) in primary care were randomised according to general practice (n=89) to one of two computer generated prompts, by the haematology laboratories in two large district general hospitals. Data were collected 12 months after the index date. The primary outcome measure was the adequacy of investigation of the cause of anaemia. Multiple logistic regression was used to analyse each binary outcome. RESULTS: Two hundred and three (47%) of 431 patients presenting to their general practitioner with an IDA were adequately managed and 140/357 (39%) of patients who were otherwise fit for investigation had no tests at all. Twenty one (17%) of 125 patients who did have adequate investigation at the time of presentation were found to have colorectal cancer. Only 30% of patients had a confirmed diagnosis within 12 months. The prompt did not affect the level of investigation (odds ratio 0.88, 95% confidence interval (CI) 0.60 to 1.29, p=0.52). The initial prescribing of oral iron was improved (odds ratio 2.19, 95% CI 1.27 to 3.77, p=0.005), but not the documented prescribing of a full therapeutic course or the use of follow up blood counts. CONCLUSIONS: The investigation and management of IDA presenting in general practice remains inadequate and is not improved by a simple management prompt.