Duplicate prescriptions: an aid to research and review.

We describe a method of studying patterns of prescribing and related morbidity in general practice. Prescribing data were automatically duplicated onto a ;no-carbon-required' prescription-pad. Additional information about diagnosis and indications for each drug, an indication of whether the drug was newly prescribed or a repeat, and a patient identification code were entered onto the bottom copy. A computer was used to process the data, which were gathered over a period of seven months.The method offers an efficient means of collecting data which can be applied by individuals or groups of doctors to improve patient care and help achieve rational prescribing.