The purpose of these studies was to analyze the consequences of long-term collagen gel contraction on fibroblast growth and metabolic activity. After 4 weeks, floating gels were 98% contracted, and attached gels were 94% contracted. During this culture period, fibroblasts in floating gels regressed significantly compared to fibroblasts in attached gels, although the cells remaining in the floating gels were viable. In attached gels, fibroblasts were bipolar; whereas in floating gels, fibroblasts were stellate. Therefore, differences between survival of fibroblasts in attached and floating collagen gels might depend on cell shape. Similarly, extracellular matrix organization and its influence on cell shape might control fibroblast proliferation in granulation tissue. During long-term culture of fibroblasts in contracted collagen gels, 70%-80% of the starting collagen was degraded. Collagen synthesized by cells in 4-d cultures was mostly procollagen secreted into the medium. On the other hand, collagen synthesized in 4-week cultures was processed to alpha (I) chains and incorporated into the matrix. There also were other differences between the proteins synthesized by fibroblasts after short-term and long-term culture in contracted gels. These findings show that fibroblasts in long-term collagen gel cultures express unique growth and biosynthetic characteristics.