Total pressure measurements at 313.15 K are reported for binary systems of methanol with each of seven pentanol isomers : 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, 2-methyl-2-butanol, 3-methyl-1-butanol, and 3-methyl-2-butanol. The results were obtained using a Van Ness apparatus and were fitted to the four-suffix Margules equation using Barker’s method. The four-suffix Margules equation represents the data to within an average of approximately 0.02 kPa.