Fourteen patients with ipsilateral pleural effusion from non small cell cancer of the lung, 10 of them with generalized metastasis, were treated with local application of HLI-alpha in addition to other symptomatic treatment. Cytology of pleural fluid at the beginning of treatment yielded cancer cells in all but one. HLI-alpha, 2 x 10(6) International Units (I.U.) diluted in 20 ml of distilled water was injected intrapleurally each time. The mean survival of the HLI-alpha treated patients, measured from the first treatment of the pleural effusion, was 10.8 months. The performance status improved in 9 patients following HLI-alpha treatment. The pleural effusion eventually ceased accumulating in all patients. To judge from cytology of tapped pleural fluid, the cancer cells disappeared during treatment with HLI-alpha in 11 patients.