Mastocytoma is a rare tumour in cats, which represents only 1–6% (Weller, 1978) or 1–9% (Moulton and Harvey, 1990) of all neoplastic forms. Mastocytoma occurs in older subjects without breed or sex predisposition. However, it seems to be more common in Siamese cats (Jubb et al., 1985). Mastocytoma in cats occurs in either a cutaneous or visceral form. The latter is differentiated into either systemic (associated more or less with mastocytaemia), or intestinal. As mastocytoma is rare in cats, especially in the intestinal form, it is of interest to present this work which presents the result of physical and instrumental examinations, as well as histopathological findings. These allowed diagnosis of visceral mastocytoma in three cats, two of which had the systemic form, while the third had the intestinal form.