High heat polyethersulfone compositions are provided which possess unexpectedly high glass transition temperatures. The polyethersulfone compositions comprise structural units derived from phthalimide bisphenols such as 3,3-bis(4 -hydroxyphenyl)-N-phenylphthalimide, and structural units derived from at least one biphenyl-bissulfone such as 4,4'-bis((4-chlorophenyl)sulfonyl)-1,1'-biphenyl. The novel polyethersulfone compositions may further comprise structural units derived from one or more biphenols such as 4,4'-biphenol, bisphenols such as BPA, or other electrophilic sulfone monomers, such as bis(4-chlorophenyl)sulfone. In one embodiment, the polyethersulfone composition of the present invention comprises structural groups derived exclusively from 3,3-bis(4-hydroxyphenyl)-N-phenylphthalimide, and 4,4'-bis((4-chlorophenyl)sulfonyl)-1,1'-biphenyl and exhibits a single glass transition of greater than 300.degree. C.