The stability of phases in the (Y1-xPrx)2Ba4Cu7O15-δ (Pr-doped 247) system with x= 0 to 1.0 was investigated. The samples in the Pr-doped 247 series were prepared at 990°C under 20-24 bar of oxygen atmosphere, followed by long time annealing at 300°C under 120 bar of oxygen pressure. Nearly single-phase samples were obtained only for x≤0.6-0.7 based on X-ray diffraction data. The lattice parameters of the Pr-doped 247 samples increased monotonically with increasing x due to the larger size of Pr. The superconducting transition temperature (Tc) of Pr-doped 247 samples determined from resistive measurements and field-cooled magnetization was found to be in good agreement and decreased from 88 (x= 0) to 21K (x= 0.6) with increasing x.