GH has a strong influence on body composition. However, the effects of GH deficiency in adults on water compartments are not well understood. Therefore, extracellular water (ECW) and total body water were independently determined by deuterium and bromide dilution and by bioimpedance spectrometry in GH-deficient (GHD) adults and compared to those in controls, matched for age, sex, body weight, and height. The results show that the percent body fat was significantly (P < 0.05) higher, and total body water and intracellular water (ICW) were significantly lower in GHD adults for males, females, and both sexes combined. ECW was not significantly different between the two groups. ECW/ICW in GHD adults (0.42 +/- 0.03) was significantly (P < 0.01) higher than that in controls (0.39 +/- 0.02). There was a significant positive relation between the ECW/ICW ratio and the percent body fat. These results were confirmed by the bioimpedance spectrometry measurements.