Osteoblasts from involved and noninvolved sutures and normal membranous bone in patients with premature unilateral coronal synostosis were harvested and grown in tissue culture. The cultures were characterized to establish specific basal metabolic parameters of cellular growth and the production of metabolites, including osteocalcin, alkaline phosphatase, platelet-derived growth factor, epidermal growth factor, tumor necrosis factor-α, and DNA. In addition, metabolic responses to two provocative bone trophic agents, parathyroid hormone and 1,25dihydroxyvitamin-D3 were ascertained. Osteoblasts from involved sutures (involved bone) exhibited altered indices of cellular metabolism when compared with osteoblasts derived from noninvolved sutures (noninvolved bone) in a basal state and when exposed to parathyroid hormone and vitamin D3 (p ≤ 0.05). Involved osteoblasts produced significantly more osteocalcin and significantly less alkaline phosphatase than noninvolved osteoblast-derived cultures (p ≤ 0.05). Secretion of plateletderived growth factor and epidermal growth factor was also altered in the involved osteoblasts compared with the noninvolved osteoblasts (p ≤ 0.05). Secretion of tumor necrosis factor-α was not significantly different between involved and noninvolved osteoblastderived cultures.