Structural, magnetic, and calorimetric properties are reported for the La12xPrxBa2Cu3O7 solid olution. The structure remains orthorhombic with lattice parameter increases from a50.3872, b 50.3927, and c51.1709nm for PrBa2Cu3O7 to a50.3903, b50.3944, and c51.1801nm for LaBa2Cu3O7. Substitution of Pr for La depresses Tc from 90 to 52K for La0.5Pr0.5Ba2Cu3O7, which was reported to be a nonsuperconductor. The Pr antiferromagnetic ordering temperature TN decreases monotonically from 18K for PrBa2Cu3O7 to 6K for La0.8Pr0.2Ba2Cu3O7. Thus there is a large range of coexistence of superconductivity and antiferromagnetism for 0.2<x<0.5. The superconductivity and anomalous Pr ordering will be discussed with the R12xPrxBa2Cu3O7 systems R5Y, Nd-Lu.