Quantifying effects of husbandry conditions on the physiology of zoo animals is an important part of assessing husbandry success. This study investigates fecal glucocorticoid (GC) levels of pileated gibbons (Hylobates pileatus) and its relationship to specific life-history variables and environmental factors. Following the validation of an enzymeimmunoassay for the measurement of 5-reduced 3α,11ß-dihydroxy cortisol metabolites to reliably assess GC output in the pileated gibbon, we collected fecal samples over several days from all 36 (22.14) European adult pileated gibbons located in 11 institutions and compared GC levels with respect to intrinsic individual parameters, husbandry, behaviour and breeding history. Hand-reared animals had higher GC hormone levels (p=0.043) and showed more behavioural abnormalities than parent-reared animals (p<0.001). Furthermore, non-reproducing gibbons living in a pair without infants had higher GC concentrations than gibbons living in a family (p=0.039). With respect to environmental factors, a large size of the inside enclosure (p=0.011) and the existence of visual protection from visitors (p=0.003) was associated with lower fecal GC output. The data indicate that rearing and housing conditions appear to be correlated to GC levels in pileated gibbons housed under captive conditions. This knowledge will hopefully support the future management of the species in captivity and thus lead to a more successful breeding of this endangered primate.