Vitamin D status, measured as serum calcidiol concentration, was studied in a group of 273 recently hospitalised patients at Aker University Hospital and compared to a group of 98 persons living in their own homes, all living in Oslo and all above 70 years of age. We found lower serum calcidiol concentrations in the hospital group than among people living in their own homes, in men as well as in women (mean +/- SD, 40.4 nmol/l +/- 23.2 vs 59.6 nmol/l +/- 28.9 in men and 37.5 nmol/l +/- 22.6 vs 48.5 +/- 20.3 in women). 34% of the men and 49% of the women in the hospital group had vitamin D deficiency (se. calcidiol < 20 nmol/l). There was no seasonal variation in the hospitalised group; the group living at home did show seasonal variations, with highest levels in late autumn (62.2 nmol/l) and lowest levels in February (42.7 nmol/l). The low levels of calcidiol concentration may contribute to the high prevalence of hip-fracture among elderly in Oslo.