Physico-chemical properties of alkyl-lead compounds, namely aqueous solubility, octanol-water partition coefficient (K-ow), vapour pressure and Henry's Law constant, have been determined, Vapour pressures of trialkyl-lead salts at different temperatures were measured by a gas-saturation technique in which air was passed slowly through a glass column packed with pure solid alkyl-lead compounds, K-ow of tetra-alkyl-lead (TAL) and trialkyl-lead (TriAL) were determined under different salinity and pH conditions, and the latter were related to the species (R(3)Pb(+), R(3)PbOH(0) or R(3)PbCl(0)) dominating under a particular set of conditions, Regression calculations incorporating melting point corrections relate water solubility to K-ow, and provide a means of estimating either parameter for a wider range of compounds.