Epoxide resins are cured by heating with a hydroxyphenylurea of formula ##STR1## where R.sup.2 denotes --NH.sub.2, --NO.sub.2, --Cl, --Br, or alkyl, p denotes zero, x and y each denote zero or 1, and the sum of x+y is 1. Such hydroxyphenylureas may be used alone, as accelerators for heat-curing with other agents such as dicyandiamide, melamine, and carboxylic acid hydrazides, or may be used as the primary curing agent with promoters such as dicyandiamide, melamine, and carboxylic hydrazides.