I review the principal experimental findings about superconductivity,
suppression thereof, and related properties of RE_{1-x}Pr_xBa_2Cu3O7 in a
decision-tree manner, eliminating the models substantially incompatible with
established experimental facts, eventually focussing on the pf\sigma
hybridization models and listing on a verbal level the interpretations of the
existing experiments as they emerge from such models.Comment: Talk given at the HTS-99 conference, Miami, 1999. Requires
aipproc.sty, epsfig. V.3, correcte