Excess molar volumes, V-m(E), of six binary mixtures of ethanoic acid and propanoic acid with butan-2-ol, methyl-2-propanol, and 2-methyl-butan-2-ol were obtained from density measurements over the entire range of compositions at T = (293.15 to 333.15) K. A sigmoidal behavior was observed for the V-m(E), values of ethanoic acid with butan-2-ol and 2-methyl-butan-2-ol, and negative V-m(E) values were obtained for the binary mixture of ethanoic acid with methyl-2-propanol at T = (293.15 to 303.15 or 313.15) K. But the effect of the rising temperature is not the same for these mixtures. For the mixtures containing propanoic acid with alcohols the V-m(E), values were negative and become more negative with increasing temperature over the entire range of compositions and temperatures except for the mixture of propanoic acid with methyl-2-propanol. Totally unregulated behavior was observed by a mixture of carboxylic acids with alcohols at different temperatures.