106 cases of cutaneous mucinosis in dogs and cats were analized by a histological and histochemical study. Except mucinosis of Shar-Pei, most of cutaneous mucinosis are clinically inapparent. Their histological and histo-chemical study shows that they constitute a heterogeneous group that can be subdivided as in man in primary and secondary mucinosis. In diffuse primary mucinosis, it is possible to distinguish the forms associated to fibroblastic hyperplasia and/or activation (mucinosis of Shar-Pei, papular mucinosis) from those non-associated to these lesions (myxedema, scleredema). The dermal mucinosis linked to canine hypothyroidism is characterized by discrete deposits of hyaluronic acid in sub-epidermal connective tissue and loose reticular connective tissue. The mucinosis of Shar-Pei results from massive accumulation of hyaluronic acid and to a lesser extent of chondroitins 4 and 6 sulphate and dermatan sulphate in dermis and hypodermis. On account of its frequency and its intensity, this mucinosis can be a good model, particularly to study the role of fibroblasts in its formation.