Analyses of New World skeletal populations for the presence of erosions and other osseous alterations and their character, distribution, and radiologic appearance shows that osteoarthritis is predominantly a disease of animals raised in artificially constrained environments. Primary calcium pyrophosphate deposition disease (CPPD) was also found only in artificially constrained animals, although hyperparathyroidism (overproduction of parathyroid hormone) may have been responsible. CPPD was observed once as a secondary phenomenon, complicating another form of arthritis in free-ranging animals. Limited in occurrence to two genera,Alouatta andCebus, the frequency of spondyloarthropathy was similar to that noted in humans and significantly lower than that observed in gorillas and chimpanzees. The many dichotomies ofCebus andAlouatta place them almost at opposite ends of the New World monkey spectrum, making a common susceptibility factor difficult to identify.