The body density of 50 healthy, young, white men was determined by underwater weighing, allowance being made for the pulmonary residual volume determined by the open-circuit nitrogen-dilution method. Skinfold thickness was measured with the MNL caliper at each of seven sites. The skinfold measurement over the front of the thigh had the highest individual correlation with body density and the highest multiple correlation of two skinfolds with density was given by those over front of thigh and below inferior angle of scapula. The multiple regression equation is given for prediction of body density from these skinfold measurements. The thickness of subcutaneous fat was measured with an ultrasonoscope at the same seven sites. Once again the measurement on the front of the thigh had the highest correlation with body density. The highest multiple correlation given by two ultrasonic measurements was from front of thigh and iliac crest. The multiple regression equation is given for prediction of body density from these measurements. The percentage by weight of fat in the young South African men was found to be similar to that of young men in some other countries.