Some antioxidant activities of extracts of irradiated black pepper (Piper nigrum) were evaluated. The ground black pepper was exposed to gamma-irradiation at doses from 5 to 30 kGy. The effect of irradiation on antioxidant properties of black pepper extracts was investigated by these methods: radical scavenging effect on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals, determination of reducing power, thiobarbituric acid reactive substances assay and electron paramagnetic resonance spectroscopy (EPR). Irradiation resulted in a decrease of DPPH antiradical activity of black pepper extracts according to dose of irradiation. Reducing power was not changed by action of irradiation. Very important and sensitive differences in antioxidant activity of irradiated black pepper were investigated by EPR spectrometry and thiobarbituric acid method.