To assess the efficacy and acceptability of vitamin D-fortified liquid milk in the management of hypovitaminosis D we carried out a double-blind, randomized, controlled trial on 51 community-based, elderly subjects with serum 25 hydroxyvitamin D (25OHD) levels of less than 12.9 ng/ml (normal range 10-80 ng/ml). Each subject had a dietary assessment, mental test score, outdoor score, serum 25 hydroxyvitamin D level, and a general biochemical screening at baseline in April 1993 which was repeated in September 1993, April 1994, and September 1994. All subjects received 500 ml of milk per day, delivered to their homes in specially manufactured, blank, tetrapak cartons, from June 1993 to June 1994: 23 subjects received unfortified milk (control group) and 28 subjects received fortified milk (active group). Our results showed a baseline mean 25OHD level in the active group of 9.6 (range < 5.5-12.7) ng/ml and in the control group of 10.0 (range < 5.5-12.9) ng/ml (P < 0.4). One year later the mean 25OHD level in the active group had risen significantly from its baseline to 18.5 (range 9.6-26.7) ng/ml (P < 0.001) and was significantly different from the control group with a 1-year mean of 12.7 (range < 4-24.1) ng/ml (P < 0.001). Serum calcium levels in the active group also showed a significant rise over the 1-year period (P < 0.001) whereas those in the control group did not. We conclude that vitamin D-fortified liquid milk is a safe, effective, and acceptable method of administering vitamin D to the elderly, community-based population.