Testosterone (T) and cortisol (C) were determined in serum and saliva, sampled simultaneously, from triathletes and karate athletes, in order to determine the T:C ratios in those body fluids and the relationship between them, as well as to assess the salivary T:C ratio as a measure of the so-called anabolic-catabolic index. Mean salivary T:C (value (1.67 +/- 0.85) was nearly 3-fold lower than that obtained for serum (4.87 +/- 1.86). Salivary and serum values were strongly correlated with one another (r = 0.874, p < 0.001) but the relationship depended on the range of cortisol concentrations in serum, the slope of the salive-serum regression line being significantly lower for serum cortisol concentrations over 600 nmol.l-1 than for concentrations below that value (0.305 and 0.380, p < 0.05, respectively). It has been concluded that the salivary T:C ratio, based on values reflecting the levels of biologically active fractions of T and C in circulation, is a better measure of metabolic equilibrium conditioned by those hormones than the corresponding ratio obtained from total concentrations in serum.