The solvent extraction of Cu(II) from 0.10 mol/dm(3) sulphate medium by purified cyanex 272 (bis-2,4,4-trimethylpentylphosphinic acid, BTMPPA, HAD dissolved in distilled aliphatic kerosene has been investigated. The equilibration time is less than 15 min. The distribution ratio is found to decrease appreciably with equilibrium CLI(II) concentration in the aqueous phase, particularly, at its higher concentration region indicating some sort of association of Cu(II) species in either of the phases. The pH and the extractant concentration dependences oil distribution ratio are I and 1.2, respectively. The distribution ratio is almost independent of sulphate ion concentration in the aqueous phase. The Delta H value is 27.3 9 +/- 0.5 kJ/mol. The 60% extraction equilibrium reaction is suggested to be: CuHSO4+ + H(2)A(2(o)) reversible arrow CuHSO4 A. 0.5 H(2)A(2(o)) + H+ and some 40% extraction is likely to occur via the reaction, CuHSO4+ + 1.5 H(2)A(2(o)) reversible arrow CuHSO(4)A.H(2)A(2(o)) + H+ satisfying the extractant dependence of 1.20. The apparent extraction equilibrium constant (K-ex) is estimated to be 10(-3.15). The loading capacity of BTMPPA is 13.47 g Cu(II)/100 g BTMPPA. Among H2SO4, HCl and HNO3 solutions as stripping agent, 1 mol/dm(3) H2SO4 Solution is found to be the best; 99.6% Cu(II) in the organic phase can be stripped off in three stages (O/A = 1 in each stage). The Cu(II) distribution ratio measured at pH = 4 in different diluents does not show good correlation with the cross-sectional area of BTMPPA molecules at interfaces formed by different diluents at pH 0.80.