Three periarticular connective tissues from normal rabbits were examined for collagenolytic activity. Enzyme activity was secreted by cultures of anterior cruciate ligament (ACL), medial collateral ligament (MCL) and patellar tendon (PT). A lag period of six days or more was often observed prior to the detection of active collagenase. We attributed this to the presence of an excess of inhibitor in the early days of culture. We quantitated the amount of enzyme and inhibitor produced in 13 days. The levels of collagenase in the ACL and MCL were comparable. The PT, however, consistently secreted more enzyme than the two periarticular (ACL and MCL) ligaments. The reaction products were analyzed for all three collagenases and compared to those generated by the rabbit skin enzyme. We observed the characteristic TCA and TCB collagen fragments for MCL and PT enzymes. Collagen cleavage by the ACL cultures resulted in a product with a molecular weight intermediate between the alpha 2 chain and the TCA piece. These data suggest that quantitative and qualitative differences exist in the ability of these similar connective tissues to degrade collagen.