Anaemia is a common problem in primary care. It can be a symptom of an underlying disease such as a malignancy, and should therefore not be ignored. The diagnosis of anaemia is laboratory-based and is defined as a haemoglobin concentration below the lower reference value. The reference values are currently under debate; some authors argue that the WHO lower reference values are incorrect and should be replaced by higher values. Algorithms for requesting laboratory tests can be applied as a guide to the classification and diagnosis ofanaemia. The Dutch College of General Practitioners has issued such a flow chart which is based on Wintrobe's classification and in which the red cell volume is a central value i.e. the 'mean corpuscular volume' (MCV). An alternative flow chart has been proposed which starts with the determination of the ferritin concentration. However, neither of these algorithms is always practical. They often do not lead to a diagnosis, and combined diagnoses may not be accounted for. In general practice, the initial diagnosis of anaemia could be based on a reliable haemoglobin measurement which would establish if anaemia is or is not present. Consequently, a simple laboratory diagnosis algorithm could be applied to frequently occurring causes of anaemia, such as iron deficiency. Should the cause be a rarer one, then a specialist should be consulted.