Thermodynamic properties of lead species in aqueous solution are collected. The chemical equilibria between various forms of Pb(II) are considered. The speciation diagrams for the equilibria 4[PbOH]+(aq) ⇄ [Pb4(OH)4]4+(aq) and 2[Pb3(OH)4]2+(aq) ⇄ [Pb6(OH)8]4+(aq), and the thermodynamic activity - pH diagram of Pb(II) species are plotted. Basic chemical and electrochemical equilibria for lead are calculated. The potential - pH diagram for Pb - H2O system is revised.