Two-phase i-heptanol/water systems are studied for the isomers i = 1 to 4. Interfacial tension data, measured mainly by the spinning-drop method, are reported as a function of the temperature together with density differences between the two mutually saturated phases. The solubilities are measured for each system at 20 degrees C, a temperature at which the Gibbs adsorptions are also determined, It is shown that the three sets of data are consistent with each other.