The present disclosure describes three-dimensional printing kits, systems for three-dimensional printing, and methods of three-dimensional printing. In one example, a three-dimensional printing kit can include a particulate build material and a binding agent. The particulate build material can include metal particles. The binding agent can include a polyhydroxy polyol and a water-dispersible blocked polyisocyanate having multiple blocked isocyanate groups. The blocked isocyanate groups can include a blocking group bonded to the carbon atom of the blocked isocyanate group through a labile bond breakable by heating to a deblocking temperature. Breaking the labile bond can produce a released blocking group reacted with hydrogen and an isocyanate group.