The excess molar enthalpies for (ethanediol, or 1,2-propanediol, or 1,2-butanediol + water) have been measured at five different temperatures over the whole composition range in an LKB flow microcalorimeter. A flow-mix cell has been developed and used for the measurements. All the mixtures exhibit negative excess enthalpies. The moder parameters of the two group-contribution models EBGCM and modified UNIFAC of Weidlich and Gmehling were fitted with the experimental data and the calculated results are compared with the experimental data.