Basal PC secretion in the type II pneumocytes from bronchitic rats was the same as that in the type II pneumocytes from normal rats. Neutrophils activated by opsonized zymosan or PMA, stimulated PC secretion in type II pneumocytes without causing any cell damage. The stimulation required close accession or attachment of neutrophils and type II pneumocytes and was not affected by the pretreatment with either SOD, catalase, AA861 or alpha 1-antitrypsin.