To investigate the role of drugs in the rising incidence of fractures of the femoral neck in the elderly a case-control study inquiring about the use of prescribed drugs was carried out. The drug histories of 102 patients with femoral neck fractures were obtained from general practice records and compared with those of 204 controls matched for age and sex from the same practices. At the time of fracture 41 patients with fractures and 126 controls were receiving at least one prescription (relative risk of fracture of the femoral neck in patients taking drugs = 0.42, p = 0.0006). For all types of prescribed drugs except antibiotics the risk of fracture of the femoral neck was less in patients taking drugs than in those not doing so, and this was true at all times in the year before fracture. Six patients with fractures were receiving thiazide diuretics compared with 37 controls (relative risk 0.28, p = 0.004). These results indicate that, contrary to popular belief, drugs that sedate or that impair postural control are not important factors in fractures of the femoral neck. The results are consistent with the hypothesis that the hypocalciuria induced by thiazides protects against fracture, but the degree of protection is not significantly greater than that associated with other drugs.