The extraction of zinc(II) by Cyanex 923 (phosphine oxides mixture) in Solvesso 100 from hydrochloric acid solution has been investigated. The extraction reaction is exothermic. The numerical analysis of metal distribution data suggests the formation of ZnCl2.L-2,HZnCl3. 2L and H2ZnCl4. 2L(L = ligand) in the organic phase with formation constants K-ext = 4.1,5.6 x 10(9) and 6.7 x 10(9), respectively. The results obtained for zinc(II) distribution have been implemented in a solid-supported liquid membrane system. The influence of source phase stirring speed, membrane composition and metal concentration on zinc transport have been investigated.