Isothermal P, x data at 413.65 K, excess enthalpies at 323.15, 363.15, and 413.15 K, and azeotropic data are presented for binary systems containing benzaldehyde, benzene, toluene, and phenol. Reliable information about the real behavior of systems including these components is very important for various chemical processes, e.g., for the production of phenol by toluene oxidation. Furthermore, these data will be used for the revision, extension, and further development of the group contribution method modified UNIFAC (Dortmund). The vapor-liquid equilibrium (VLE) data of four systems were measured using a static apparatus. In the case of the system benzaldehyde + phenol, azeotropic data were determined by distillation. For all systems, the corresponding experimental excess enthalpy (HE) data were determined with the help of an isothermal flow calorimeter. For the simultaneous description of VLE and HE data, the NRTL model was used.