The distribution of water between extracellular fluid (ECF; measured by the inulin dilution technique) and intracellular fluid (ICF; calculated as the difference between total body water, which was measured by the deuterium dilution technique, and ECF) was measured in 12 healthy subjects. The results were compared with predictions made by anthropometry and whole body impedance obtained at 1kHz (Z(1)) and 50 kHz (Z(50)). Z(1) and Z(50) were also measured in 82 health subjects and 27 patients without clinically detectable oedema, and in 10 patients with oedema. Anthropometry and height(2)/Z(1) showed similar correlations with inulin space (r = 0.64, SEE = 1.74 L and r = 0.65, SEE = 1.75 L respectively). The ratios of Z (1)Z (50) in oedematous patients (1.03 +/- 0.02), which were universally lower than those obtained in normal subjects (1.18 +/- 0.04), overlapped with those obtained in patients without oedema (1.11 +/- 0.05). The study suggests that in this group of normal subjects low frequency bioimpedance measurements are not superior to anthropometric estimates of ECF. They also suggest a limitation in the use of the dual frequency bioimpedance meter to distiguish between patients with and without oedema.