The anterior cruciate ligament (ACL) has poor healing responses compared with those of the medial collateral ligament (MCL). It has been implied that this is partially due to the poor reparative capacity of ACL cells for ligament injury. The present study was designed to elucidate the reparative capacities of human ACL and MCL cells by investigating their cellular properties and their responses to growth factors. Human ACL and MCL were obtained from seven fresh human cadavers. The cells were isolated from each tissue, and primary cultures were used for the examination. The growth rates of all the human ACL cells were lower than those of the human MCL cells; consistent with this, the doubling time of the ACL cells was 30 +/- 7.4% longer than that of the MCL cells. The chemotactic migration of human ACL cells was 33 +/- 8.1% slower and the synthesis of DNA and collagen in human ACL cells was 29 +/- 6.3% and 31 +/- 9.7% lower, respectively, in comparison with those of MCL cells. Cellular responses, in terms of DNA synthesis, in human ACL cells to either basic-fibroblast growth factor (1.0 and 10.0 ng/ml) or transforming growth factor-beta (1.0 ng/ml) were lower than those of human MCL cells. However, no differences in the cellular responses in terms of collagen synthesis were found. Composite data show that human ACL cells have poorer cellular properties and lower responses to growth factors compared with those of human MCL cells, which suggests that the reparative capacity of human ACL cells may be poorer than that of human MCL cells.