The results of studies on the dielectric polarization for the whole range of concentrations of 2-pyrrolidinone ( -butyrolactam) in benzene as a function of temperature (20-50 °C) at 1,5 kHz are presented. The results were interpreted by assuming a model of monomer + dimer + tetramer equilibrium. The formation constants for dimers (K2) and tetramers (K4) as well as the molar enthalpies for hydrogen bonds N-H-0=C in these associates (-2 = 15.2 kJ/mol and -AH4 = 17.4 kJ/mol) were calculated.