The extraction of Cd(II), Cu(I1) and Zn(I1) from 0.1 mol dm-$ aqueous nitrate solutiona with bis(2,4,4-trimethy1pentyl)phosphinic acid (HBTMPP) dissolved in Isopar-H has been studied with relation to the total extractant concentration, the equilibrium pH and the total metal concentration in the aqueous phase.