Of 65 patients presenting with pulmonary eosinophilia to one Respiratory Unit during a 20-year period, 12 (18%) had systemic features associated with their pulmonary disease. Eleven had fever, three night sweats, three arthralgia, three vasculitic rashes and two weight loss. Anaemia, myalgia, peripheral neuropathy, mononeuritis, pericardial effusion and photosensitivity rash were each recorded in single patients. None had evidence of hypersensitivity to drugs, helminthes or other allergens. Ten of the 12 patients could be classified as cryptogenic pulmonary eosinophilia and two as Churg Strauss syndrome. Ten were female. The maximum recorded eosinophil counts were higher in the 12 patients with systemic features compared with the remaining 53 patients [mean (SD) 5613 (3883) vs. 2359 (3046) x 10(6) 1(-1), P < 0.02], whereas both asthma and recurrent episodes of eosinophilia were significantly less common. Steroid therapy achieved a good clinical response and radiological clearing in the majority of patients. All 12 patients were treated with prolonged duration oral prednisolone [mean (SEM) dose 8.5 (3.8) mg day-1 duration 5.5 (1.3) years]. The two patients with Churg Strauss syndrome required azathioprine in addition to long-term prednisolone. There were no deaths and currently four patients are off all steroids and six receive less than 5 mg day-1. During a median follow-up period of 11 years, there was no significant decline in FEV1 or VC, measured as percent predicted values. Persistent radiographic abnormalities consistent with fibrosis or bronchiectasis were not seen.(ABSTRACT TRUNCATED AT 250 WORDS)