In clinical records many items are handwritten and difficult to read. We examined clinical histories in a representative sample of case notes from a Spanish general hospital. Two independent observers assigned legibility scores, and a third adjudicated in case of disagreement. Defects of legibility such that the whole was unclear were present in 18 (15%) of 117 reports, and were particularly frequent in records from surgical departments. Through poor handwriting, much information in medical records is inaccessible to auditors, to researchers, and to other clinicians involved in the patient's care. If clinicians cannot be persuaded to write legibly, the solution must be an accelerated switch to computer-based systems.