Immunohistochemical localization of chondroitin sulphate and dermatan sulphate proteoglycans (PGs) was observed in 70 tumour tissues, using monoclonal antibodies 9A-2 and 3B-3 raised against core molecules obtained from chondroitin sulphate PG by chondroitinase ABC-treatment. They recognize a stub of delta Di-4S and delta Di-6S binding to core protein via a linkage tetrasaccharide, respectively. The antibody 6B6 raised against dermatan sulphate PG obtained from an ovarian fibroma capsule in our laboratory was also used. The interstitial fibrous elements, so-called 'specific stroma' within the cancer cell nests contained chondroitin 4-sulphate PG as revealed with 9A-2, whereas the surrounding connective tissue and the preexisting fibrous connective tissue involved in the tumour growth consisted of dermatan sulphate PG with a considerable amount of chondroitin 4-sulphate PG. Chondroitin 6-sulphate PG as revealed with 3B-3 was located in the connective tissue proliferating from blood vessels and muscle tissue in association with the invasive growth of tumour cells. Chondroitin 6-sulphate PG was also observed in the basement membrane components of some tumours. In non-epithelial tumours (fibrogenic, chondrogenic, osteogenic and neurogenic tumours), chondroitin 4-sulphate was in fibrous portions. When collagenization and hyalinization progressed, dermatan sulphate PG was observed to increase in quantity.