An ebulliometer was used to measure pressure-temperature-liquid composition (PTx) data on twelve mixtures of ethylene glycol + 1,3-propylene glycol (and the pure components) between 120 degrees and 185 degrees C. Bubble-point data were measured at five pressures from 6.67 kPa to 40.0 kPa. A Redlich-Kister G(E) model fit isotherms at 125 degrees, 150 degrees, and 175 degrees C via Barker’s method with an average standard error of 1.2 % in pressure. The system exhibits moderate positive deviations from ideality (derived gamma(infinity) = 1.1 - 1.8) which decrease with increasing temperature. Equimolar G(E)/T values thus derived also decrease with increasing temperature which predicts a positive H-E. Mixture density data were measured in a Anton-Parr densimeter between 10 degrees and 150 degrees C. These density data show a small negative equimolar V-E at 10 degrees C that becomes positive and increases linearly with increasing temperature. The system ethylene glycol + 1,3-propylene glycol belongs to the class of mixtures where G(E)>0, H-E>0, and TSE>0. These excess-function data suggest that (1-1) or (2-2) hydrogen-bonding of ethylene glycol or 1,3-propylene glycol persists in the mixture to a greater extent than (1-2)-type hydrogen-bonding of ethylene glycol + 1,3-propylene glycol.