Thirty-eight consecutive obese persons were treated as outpatients. The treatment commenced with VLCD formula diet NUPO (females 388 kcal, 1600 kJ, 56 g protein; males 446 kcal, 1864 kJ, 69 g protein). VLCD had no untoward effects and was continued for as long as the patient would accept. After that the formula diet was supplemented with ordinary items of food and drink to the level of 1000 kcal (4200 kJ) for women and 1100 kcal (4600 kJ) for men. After 5 months the data were analyzed separately according to the duration of VLCD: group 1 (n = 20): VLCD for less than 2 months, and group 2 (n = 18): VLCD for 2 months or more. The two groups were comparable with regard to height, absolute weight and percentual overweight, but group 2 was somewhat older than group 1 (49.5 vs 38.3 years, P less than 0.01). Group 2 lost significantly more weight, both totally (17.1 kg (7.8-40.1] and on VLCD alone (12.3 kg (4.1-28.8], than group 1 (8.7 kg (-1.1 to 19.1), P = 0.008; and 7.3 kg (0.9-18.2 P = 0.01). Weight losses in both groups eliminated or strongly reduced the need for a wide variety of expensive drugs: antidiabetics, diuretics, antihypertensives, analgetics, etc. It is concluded that VLCD is an effective and encouraging way of starting a dieting program, and that it should be continued for at least two months, as the length of the initial VLCD period related significantly to the amount of weight eventually lost.