The irregular solution behaviour of paracetamol was observed in two solvent systems: ethyl acetate-methanol; water and normal alcohols. The extended Hildebrand solubility approach was used to process the solubility data on paracetamol. The solubility parameter of paracetamol was determined from different methods of data analysis and found to be approx. 13.40 H. The parameters W and (log γ2)/A were regressed against a polynomial of δ1 of the binary mixture. The expressions allowed calculation of the mole fraction solubility of paracetamol in polar solvents. The expression for W regression was satisfactory for the determination of the solubility of paracetamol in methanol, ethanol and their mixtures, but deviated in the case of butanol and propanol. © 1992.