We report a case of systemic mastocytosis (SM) presenting as ascites and portal hypertension. The haematological picture at presentation was suggestive of chronic myelomonocytic leukaemia. Initial difficulties in making a diagnosis of SM were encountered as the cutaneous signs were atypical. The correct diagnosis was established only after tissue sections were appropriately stained for mast cells. The liver biopsy showed portal and sinusoidal mast cell infiltration, portal fibrosis and evidence of hepatic venous outflow obstruction. The disease progressed rapidly and recurrent massive ascites was a dominant problem. This case illustrates again the problems of making a diagnosis of SM especially when the clinical picture is atypical. Ascites as a presenting manifestation of SM has been reported previously in only six patients. Published cases of SM with portal hypertension or ascites or both are reviewed.