Phase diagrams for the binary systems {tri-iso-butyl(methyl)phosphonium tosylate ionic liquid (i-B3MPTOS + 1-alcohol, or n-alkane, or n-alkylbenzene} have been measured at atmospheric pressure by a dynamic method. (Solid + liquid) phase equilibria were measured for systems of alcohols (1-decanol and 1-dodecanol) and the ionic liquid and (liquid + liquid) phase equilibria for binaries containing hydrocarbons (n-hexane, n-heptane, n-octane, n-nonane. n-decane, toluene, ethylbenzene, n-propylbenzene, n-burylbenzene). The reduction of experimental data has been carried out by correlation using the Non-Random Two Liquid (NRTL) equation. The measured diagrams have been compared with analogous diagrams reported previously for systems with ionic liquids containing the symmetric quaternary phosphonium cation. The influence of the asymmetry of the cation on the phase behaviour of phosphonium ionic liquids has been discussed. (C) 2009 Published by Elsevier B.V.