The long-term clinical course of patients with primary Type II essential mixed cryoglobulinaemia is unclear as many reports fail to separate this group from patients with Type III disease. We have reviewed 13 patients with Type II essential mixed cryoglobulinaemia who presented to the Hammersmith Hospital between 1976 and 1990. All patients had a cryoglobulin level greater than 0.1 mg/ml (range 0.27-6.50 mg/ml), and characterization of the cryoglobulin in all cases revealed the presence of a monoclonal IgM kappa component with rheumatoid factor activity together with polyclonal IgG. All patients had evidence of activation of the classical pathway of complement with greatly reduced levels of C4, while C3 levels were moderately reduced in three patients. All patients had skin disease and joint symptoms were reported by nine patients, with erosive arthritis in one. Eight patients had peripheral sensorimotor neuropathy. Renal disease was observed in 10 patients, manifesting as raised creatinine level, proteinuria or haematuria. Renal tissue was examined in eight patients: in six the appearances were those of a mesangiocapillary glomerulonephritis Type I while in the other two patients there was a mesangioproliferative glomerulonephritis, in one diffuse and in the other focal and segmental. Glomerular capillary 'hyaline thrombi' were found in six biopsies, extracapillary proliferation was found in three and evidence of vasculitis was found in all eight. Liver biopsy showed macronodular cirrhosis in one patient, while a second with recurrent episodes of jaundice showed only chronic inflammatory changes. No patient was positive for hepatitis B surface antigen; however one patient had low titre anti-hepatitis B surface antibody. Normochromic normocytic anaemia was present in nine patients. Bone marrow examination was carried out in 13 patients at presentation to our unit: 10 showed no evidence of a lymphoproliferative disorder, while three suggested the presence of a non-Hodgkin's lymphoma (some years after original presentation in all three). Unusual clinical features included one patient with retinal vasculitis and one patient with severe pulmonary haemorrhage.