The vitamin D status of women with femoral neck fractures and of male and female nursing-home residents in South Australia was assessed and compared with that of ambulant normal elderly women and young male and female controls. Serum 25-hydroxyvitamin D (25OHD) was assayed with a competitive protein-binding method including a chromatography step. The mean serum 25OHD levels in the patients with femoral neck fractures (39.2 [SE 2.6] nmol/L) and in the nursing-home residents (28.9 [SE 1.3] nmol/L) were significantly lower than those in the ambulant elderly women (67.6 [SE 3.9] nmol/L) and young controls (76.9 [SE 3.7] nmol/L) (P less than 0.001 in each case). The serum 25OHD levels were unrelated to age in the normal ambulant subjects. There was a significant seasonal variation in the results of routine 25OHD assays performed in our laboratory, but no such variation was seen in the nursing-home residents. We conclude that vitamin D deficiency is common in housebound subjects, and that femoral neck fractures occur mainly in subjects who were housebound before the fracture.