A chloroform membrane system containing a given mixture of aza-18-crown-6 and palmitic acid was applied for the uphill transport of Pb2+ ions. In the presence of P2O74- ion as a suitable metal ion acceptor in the receiving phase, the amount of lead ion transported across the liquid membrane after 100 minutes is 89.1 +/- 1.3%. The selectivity and efficiency of lead transport from aqueous solutions containing other cations such as Zn2+, Cu2+, Ni2+, Co2+, Fe2+, Pd2+, and Ag+ ions were investigated. In the presence of S2O32- ion as a proper masking agent in the source phase, the interfering effects of Cu2+ ion were diminished drastically.