The effects of different light irradiations and anoxia treatment on the activity and expression of the lipoxygenases 1 (LOX-1) and 2 (LOX-2) of soybean seedlings have been investigated. A phytochrome-mediated decrease of the specific activities of both isoenzymes was found which was due to the regulation of the gene expression at the transcriptional level. The anoxia treatment of the seedlings led to a decrease of both lipoxygenase specific activities as well, but this effect was attributable to the reduction of the amount of the two isoenzymes, without changes in the steady-state levels of specific mRNAs. Therefore, light and anoxia are both regulators of soybean lipoxygenases, but their mechanism of action at the molecular level is different.