Dielectric, viscosity and n.m.r. measurements have been made on solutions of water in heptan-1-ol, cyclohexanol and 3-ethyl pentan-3-ol over the respective solubility ranges. In each alcohol there is evidence for the formation of an associated species in which four alcohol molecules are hydrogen-bonded to one water molecule. The stability of this aggregate in the primary alcohols may account for the limiting solubility of a quarter of a mole of water per mole of alcohol in the liquid state of the higher members of the series and its effect in increasing the temperature range over which the hexagonal α-phase exists in the solid state.