Serum levels of 25-hydroxyvitamin D (25OHD3), 1, 25-dihydroxyvitamin D [1, 25-(OH)2D3], PTH and osteocalcin were measured in 114 subjects living in the South of Spain (Cordoba, latitude 37.6 degrees) during early spring. Results in young healthy adults (group G1) were compared with values found in three groups of elderly subjects (mean age 77 years): healthy elderly people living at home (G2), or in a residence (G3) and chronically sick and hospitalized elderly patients (G4). Mean serum 25OHD3 was lower in the elderly groups G2 and G3 than in young adults but the lowest values were found in G4. The opposite trend was found for serum PTH. Mean serum 1,25-(OH)2D3 levels were similar in G2 and G3 to G1 but were significantly lower in G4. In a sunny country only chronically sick and hospitalized elderly patients have very low 25OHD3 levels and fail to maintain normal 1,25-(OH)2D3 concentrations despite secondary hyperparathyroidism.