Abstract: A capped poly(phenylene ether) resin composition is formed from (1) a poly(phenylene ether) compound (PPE) in which at least a portion, preferably substantially all of the hydroxyl groups have been reacted with a compound containing ethylenic unsaturation (carbon-carbon double bonds) which is further reactive with unsaturated monomers (reactively endcapped PPE) and (2) a curable unsaturated monomer composition. The composition optionally contains a polymerization catalyst; a flame-retardant compound; and fibrous reinforcement. The composition can be cured to form a laminate, and clad with copper to form a circuit board.