We investigated whether physical enhancers of low-level chemiluminescence-coumarin laser dyes C-314, C-334, and C-525--may be used to monitor interactions of lipid peroxyl radicals during lipid peroxidation in live cells. We present data demonstrating that two quinolizin-substituted coumarins--C-525 and C-334--can be integrated into HL-60 cells and successfully used as physical enhancers of chemiluminescence induced by the lipid soluble azo-initiator 2,2'-azobis(2,4-dimethyl-valeronitrile) (AMVN). Coumarins did not inhibit AMVN-induced peroxidation of membrane phospholipids in HL-60 cells, and no consumption of these coumarins occurred in the course of AMVN-induced oxidative stress. Redox status, evaluated by intracellular GSH content, remained unchanged after treatment with the coumarins. tert-Butyl hydroperoxide and cumene hydroperoxide (more hydrophilic oxidants) induced a lower chemiluminescence signal with both coumarins. Viability of HL-60 cells was not affected by coumarins both in the presence and in the absence of oxidants. Based on these results we conclude that quinolizin-substituted coumarins represent a promising class of physical enhancers of chemiluminescence for monitoring free radical peroxidation in live cells.