Compelling evidence appeared in 2002 of human exposure to a plethora of primate lentiviruses through hunting, handling of bushmeat, and/or animals kept as pets in Cameroon. To determine SIV prevalence in pet animals, an analysis of 28 sera of nonhuman primates found no SIV infection in greater spot-nosed monkeys (0/5) or chimpanzees (0/10), and a prevalence rate of 23.1% (3/13) in mandrills kept as household pets in southern Cameroon. Phylogenetical analysis based on pol-integrase region and mitochondrial cytochrome b gene showed that the newly found SIV from Mandrillus sphinx (SIVmndCM-202, SIVmndCM-211, and SIVmndCM-218) clustered significantly with SIVmnd-2. Questionnaire data were also collected to assess whether owners had experienced bites, scratches, or exposure to blood and/or body fluid. Risk to human health from cross-species transmission of the newly identified SIVmnd-2 to infect humans remains unknown.