Comparative studies were undertaken on the effects of ozone and t-butyl hydroperoxide (t-BuOOH) on alkane production, glutathione and lactate dehydrogenase (LDH) release from isolated rat lungs. Specifically, ethane and pentane production, as well as glutathione and LDH release were simultaneously determined at different time intervals from the isolated lung preparation in the absence and presence of toxic concentrations of ozone or t-BuOOH. When compared to control conditions, both toxic agents produced a marked decrease in the dry weight to wet weight ratios, reflecting the development of acute pulmonary edema. These toxic agents also caused a marked increase in the efflux of glutathione into the effluent. A much higher glutathione efflux into the effluent was observed during t-BuOOH perfusion in comparison to ozone exposure. In parallel with the enhancement of glutathione release a significant increase in ethane production was also observed during t-BuOOH perfusion. However, the production of either alkane by ozone inhalation was not significantly different from that in the control conditions. Unlike glutathione release, there was no marked increase of LDH release into the effluent following exposure to t-BuOOH or ozone. This suggests that the observed increase in glutathione release caused by t-BuOOH or ozone treatment was not associated with non-specific destruction of cell membrane integrity.