Magnetic and transport properties of rare-earth manganites La0.5Ca0.5Mn1-xGexO3 with 0≤x≤0.1 have been investigated systematically. Doping Ge at Mn sites increases the metal–insulator transition temperature (TP) from 124 to 210 K with increasing x from 0 to 0.08. The introduction of Ge severely destroys the charge-ordered state and hardly affects the ferromagnetic ordering. For low-doped samples, TP is also increased dramatically by the magnetic field, especially in the field-cooled mode. Magnetic analysis suggests the coexistence of the charge-ordered antiferromagnetic phase and the ferromagnetic phase. We propose that the proportion of the ferromagnetic phase and the charge-ordered phase can affect TP in phase-separated compounds. The phase diagram of La0.5Ca0.5Mn1-xGexO3 with 0≤x≤0.1 is presented. © 2000 American Institute of Physics.