In order to elucidate the effect of L-ascorbic acid (AsA) on the formation of pyridinoline, a mature crosslink of collagen, its content in cartilage collagen of guinea pigs supplemented with and without AsA in the growing process (4-8 weeks of age) and in the period of maturity (10-14 weeks of age) was examined. The AsA-deficient animals, for four weeks during the growing process, had a significantly higher content of pyridinoline in their collagen than the AsA-supplemented group, indicating that the depletion of AsA induced increasing contents of pyridinoline. On the other hand, in the period of maturity, the pyridinoline content in the collagen decreased with age, whereas no difference between AsA-deficient and -supplemented groups was observed. Based on these results, it is assumed that AsA affects the formation of pyridinoline, especially in the growing period.