Abstract
All data on admissions to NHS hospitals are entered into the hospital episode statistics database. We studied the data for the period 1 April 1991 to 31 March 1995, at which time diagnoses were classified according to ICD-9 (international classification of diseases, ninth revision), and extracted all records concerning cyclists, whether their injuries resulted from bicycle accidents or motor vehicle accidents (codes E8261, E810-E825 fourth digit=6). From information in the primary diagnosis field, we identified head injuries as either “fracture of vault or base of skull” (ICD-9 800, 801) or “intracranial injury” (ICD-9 850-4). We used only data concerning emergency admissions and completed first episodes.