The release of the intracellular enzymes, lactate dehydrogenase, acid phosphatase and alkaline phosphatase from chopped tissue in an incubation medium was studied. An extract of cotton dust (1mg/ml) caused a small but significant release of all three enzymes after 30 min incubation with lung, liver and heart of the mouse and guinea pig. In contrast, Enterobacter agglomerans lipopolysaccharide (LPS) at concentrations equivalent to LPS levels in the dust extract and compound 48/80 had no effect on the release of these enzymes. The dust-induced release of enzymes from guinea pig lung was attenuated by the presence of anti-inflammatory agents. The hypothesis is proposed that CDE or one of its components exerts its primary action on the lysosomal membrane to initiate the changes leading to enzyme release. The three enzymes could not be detected in the perfusate of guinea pig isolated lungs receiving bronchoconstrictor doses of the dust extract. It is believed that the enzyme release phenomenon described for the chopped tissue may be more important in contributing to the chronic effects than the acute effects of inhaled cotton dust.