The aim of this study was to investigate the effect of carazolol on the generation of the oxygen species with respect to chemiluminescence (CL) from the copper ion/H2O2 system. The reactions are carried out in buffered aqueous solution. The quantum yield of the CL from the copper ion/H2O2 system is increased by a factor of 2(-10) in the presence of carazolol. The CL spectra from the carazolol/copper ion/H2O2 system are spread through the full visible region and four emission bands are shown at maxima 480-500, 580, 640 and 700 nm. The excitation spectrum obtained from the above mentioned system shows the main maxima at around 273, 310 and 340 nm (lambda obs = 365 nm). The fluorescence emission spectrum exhibits only one maximum at 365 nm (lambda exc = 340 nm) corresponding to carazolol. The light emission decreases in the presence of several biologically important compounds which are typical scavengers of oxygen radicals and singlet oxygen (1O2). The results demonstrate that carazolol enhances the production of oxygen radicals and 1O2 under our experimental conditions. Generation of 1O2 was additionally confirmed using ESR spin trapping and spectrophotometry.