AbstractMorning and evening testosterone levels were measured in the saliva of Efe pygmies (N = 11) and Lese villagers (N = 18) living in the Ituri Forest of northeast Zaïre and compared with levels in Boston controls (N = 10). With one exception, levels in the individual Zaïrois subjects fall within the normal ranges reported for Western clinical populations. Daily variation in the Zaïrois subjects (a.m./p.m. ratio = 1.32 for Efe, 1.22 for Lese) is also comparable to both the Boston controls (1.61) and values reported by other researchers for Western subjects. Average morning levels for the Zairois subjects (420 pmol/liter for Efe, 341 pmol/liter for Lese), however, fall significantly below the average for the Boston subjects (589 pmol/liter; Efe,P<0.05; Lese,P<0.01). A correlation between morning testosterone level and height is observed for the Lese sample (r=0.76,P<0.005). Similar correlations have not been reported for Western subjects. Possible roles of acute and chronic environmental conditions in generating these observations are noted. This study demonstrates the potential utility of salivary steroid assays for investigating questions related to male gonadal function under field conditio