The phase diagram of the Bi2O3-MoO3 system was investigated with combined impedance spectroscopy, differential thermal analysis and X-ray powder diffraction measurements in the composition range 0 less than or equal to x(Mo) less than or equal to 0.156. The samples were prepared by high temperature solid state reaction to account for the high reactivity of Bi-rich melts and the sluggishness of the solid-state equilibria. At high temperatures, a fluorite-like solid solution, delta, is stable over the whole composition range, and is separated by the stability field of the liquid phase by a lens-shaped biphasic region. Below the delta phase, two compounds are stable down to room temperature (rt) at the compositions x(Mo) = 0.067 (m = 14) (C1) and x(Mo) = 0.156 (m similar to 5.4) (C2) (m = Bi/Mo). The eutectoid between pure alpha-Bi2O3 and C1 is at x(Mo) similar to 0.016 at T similar to 725 degrees C, whereas the eutectoid between C1 and C2 is at x(Mo) similar to 0.091 at T-800 degrees C.