The noncollagenous matrix proteins, composing about 10% of the organic matrix of bone, are considered important for cell matrix organization and regulation of mineralization in bone. In the present study, seven of the major noncollagenous bone matrix proteins were localized immunohistochemically in serial sections of lumbar vertebrae from 24 (12 intact and 12 ovariectomized) adult female cynomolgus monkeys (Macaca fascicularis). Osteocalcin was the only protein restricted to bone cells and mineralized bone matrix. Bone sialoprotein was present in both bone and calcified cartilage, and all the other proteins were distributed in soft tissues as well as bone. Staining for both osteocalcin and bone sialoprotein was present diffusely throughout the bone matrix, but osteonectin, osteopontin, matrix gla protein, decorin, and biglycan staining was concentrated along bone surfaces. Osteoid was negative for osteocalcin and bone sialoprotein, but all other proteins had areas of positive immunostaining within osteoid. All proteins except biglycan exhibited strong immunostaining of a subset of active osteoblasts, suggesting that they may be markers of osteoblast maturity or state of activation. The pattern of immunostaining in intact and surgically menopausal monkeys was similar, except that staining for matrix proteins concentrated along bone surfaces appeared to be more widely distributed in the surgically menopausal monkeys, probably due to the higher rate of bone formation in these animals.