Explants from rabbit anterior cruciate ligaments (ACL) and medial collateral ligaments (MCL) were utilized to compare the relative rates that fibroblasts migrate onto glass and plastic culture surfaces in vitro. During the first two weeks in culture, a monolayer of cells appeared on the periphery of all the ACL and MCL explants. From 45 to 134 hrs in culture, the mean total MCL cell count per explant was 6-12 times greater than that for the ACL on the plastic culture dishes, and this difference was even greater for the cells attached to the glass cover slides over the explants. These differences were significant at the p < .005 level. The rates of cell proliferation were quite similar for primary cultures of ACL and MCL grown in the same medium as that used for the migration assay. The large difference in cell number at early times of culture is thus due to the more rapid MCL cell migration out of the explants, and not to a difference in the rate of cell proliferation. These data support the hypothesis that differences in cell migration rate play a role in the greater healing capacity of the MCL as compared with the ACL. The assay described in this work may then be useful in assessing factors that promote wound healing.