Vapour pressures have been measured along the solid-liquid equilibrium lines for the systems phenol + hexane, phenol + heptane an 4-methylphenol + hexane. The adjusted mean association number of phenol in hexane is lambda = (2.77 +/- 0.13) and in pentane is lambda = (2.90 +/- 0.05). These results indicate that the favoured structures along the solid-liquid equilibrium are trimers, probably with the cyclic structure as in the unstable solid form, lambda = 3. The adjusted mean association number of 4-methylphenol in hexane is lambda = (3.88 +/- 0.29) and is consistent with the association number of the unstable solid form, lambda = 4.