Fifty patients recorded their peak expiratory-flow rate (P.E.F.R.) in hospital, unaided by nursing staff, five times a day for 5 days. Each patient's readings were randomly and independently checked on two occasions during this period. 69% of checked readings were accurate. Most patients kept satisfactory records as a table, but were less efficient in recording their results on a P.E.F.R. chart. Recording of P.E.F.R. by patients with respiratory disease saves nursing time and provides valuable clinical information.