The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. discovered about the signal function of coloration in male and female mandrills from our long-term studies of a semi-free-ranging colony in Franceville, Gabon and test the predictions of the Hamilton-Zuk hypothesis -that bright coloration is condition dependent, and that only individuals of superior quality will be able to express color fully -in this species. We compare measures of facial coloration in both sexes with parasite load (using fecal analysis over one annual cycle), immune status (hematological parameters), neutral genetic diversity (microsatellite heterozygosity) and major histocompatability (MHC) genotype to examine whether red coloration acts as an honest signal of individual quality in mandrills. We found that red coloration was unrelated to parasitism and hematological parameters. Red was also unrelated to genome-wide heterozygosity and MHC diversity, although specific MHC genotypes were significantly related to red. The healthy, provisioned nature of the colony and problems associated with observational, correlational studies restrict interpretation of our data, and it would be premature to draw conclusions as to whether color signals individual quality in mandrills. We conclude with some suggestions for future studies on the signal content of color in mandrills and other primates.