Luminol-dependent chemiluminescence (CL) was used to assay the effect of three antituberculous drugs [isoniazid (INH), pyrazinamide (PZA), rifampicin (RM)] on the production of reactive oxygen species (ROS) by polymorphonuclear leukocytes (PMN) isolated from blood of 5 healthy donors. Drugs were added directly to the medium in concentrations; INH 5 micrograms/ml, PZA 40 micrograms/ml, RM 7 micrograms/ml. These concentrations correspond to peak serum concentrations after usual doses. RM was found to inhibit FMLP (N-formyl-methionyl-leucyl -phenylalanine)-induced CL response of PMN, PZA did not influence the metabolic activity of neutrophils, and INH stimulated PMN CL.