The work presented here on the system C17H36-C19H40 is part of a general study concerning the syncrystallization of substances in the n-alkanes family. The two substances are isodimorphous; the phase diagram of the system shows three simple phase regions which extend over the whole composition range. These three domains are consecutively an orthorhombic solid domain (O), a rotator-type solid domain (RI) and the liquid domain (L). Both (O + RI) and (RI + L) domains are narrow loops, the first with a minimum, the second without an extremum. There is a very good agreement between the solid-liquid experimental data and the calculated diagram.