A simple inexpensive densiometric method of determining body composition was compared to a more sophisticated one. Body density (Db), lean body mass (LBM), and relative fat content (%fat) were determined for 16 volunteers, 9 men and 7 women using a simple T-bar apparatus suspended in a swimming pool, and an electronic apparatus in conjunction with a metal tank. Residual volumes (RV) used in the determinations were estimated from age and height (RV-1), held constant at 1,300 ml for men and 1.000 ml for women (RV-2), and measured by the nitrogen washout method (RV-3). No significant difference was observed between the two methods of weighing, although significant differences did exist among the RV techniques. It was concluded that a simplified method of determining body composition is acceptable for screening purposes, but long term studies might require more sophisticated techniques with RV measured at the time of weighing.