A fast curing coating composition that is adapted for use as an automotive topcoat and which upon curing forms a hard, glossy, durable coating exhibiting excellent resistance to solvents and water. The coating composition which may contain greater than about 55 percent by weight of nonvolatile solids and, exclusive of pigments, solvents and other nonreactive components, consists essentially of:(A) a polyepoxide resin having a number average molecular weight (M.sub.n) of between about 140 and about 3,000;(B) a reactive catalyst comprising at least one phosphonic acid derivative;(C) an amino resin crosslinking agent; and(D) optionally, a hydroxy functional additive.The phosphonic acid derivative is included in the composition in an amount sufficient to produce between about 0.8 and about 1.4 equivalents of acid functionality for each equivalent of epoxy functionality in the polyepoxide resin and the amino resin crosslinking agent is included in the composition in an amount sufficient to provide at least about 0.4 equivalents of nitrogen crosslinking functionality for each equivalent of hydroxy functionality included in the composition.