A series of crosslinkable maleimide-ended poly(ether sulfone)s has been prepared using a range of molecular masses. The effect of the crosslinking reaction on the glass transition temperatures (T(g)s) is observed. In the range of molecular masses studied, the T(g)s after crosslinking are predominantly dependent on the intrinsic nature of the polymer and are not dependent on the final crosslink density. However, T(g)s of partially crosslinked polymers are related to the concentration of chain-ends consumed by the crosslinking reaction.