This study was undertaken to analyze the chemical composition of the proximal tibial articular cartilage and growth plate from 1-mo-old broiler chickens. The composition was different between the two types of cartilage (weight-bearing tissue and the tissue of growth center). The dry matter and collagen contents and the ratio of keratan sulfate to sulfated glycosaminoglycan (GAG) were higher, and the total GAG uronic acid, chondroitin sulfate, hyaluronic acid, and sialic acid contents were lower in the articular cartilage hyaluronic acid, and sialic acid contents were lower in the articular cartilage than in the growth plate. Chondroitin sulfate was the major GAG, accounting for an average 96% of total GAG in both tissues. The size of chondroitin sulfate examined by gel chromatography was similar between the two tissues. The articular cartilage contained a small amount of dermatan sulfate (approximately 1% of total GAG) with low iduronic acid content (38% of total uronic acid). There was no appreciable amount of dermatan sulfate found in the growth plate. Proteoglycans were extracted from these tissues with 4 M-guanidine hydrochloride and separated by ion-exchange chromatography and gel chromatography. The uronic acid to protein ratio in the proteoglycan fraction was similar (average 2.6) between the two tissues. However, gel electrophoresis of chondroitinase-ABC digests of proteoglycan fraction showed differences in their composition.