We describe efficient electroluminescence from a terbium complex, tris-(1-phenyl-3-methyl-4isobutyryl-5-pyrozolone)-bis(triphenyl phosphine oxide) terbium (PTT). The green-emitting material possesses much higher photoluminescence efficiency compared to the commonly used green light emitter, 8-hydroxyquinoline aluminum (ALQ). The rarely observed emission from the hole transport layer,N, N′-bis (3-methylphenyl)-N, N′-diphenyl-benzidine(TPD) of the device ITO/TPD/PTT/Al proves that PTT also is a good electron transporting material. The ITO/TPD/PTT/ALQ/Al device shows luminance up to920cd/m2at a drive voltage of 18 V and a luminous efficiency of 0.51 lm/W at a current density of 0.70mA/cm2,which are up to now the highest among devices using rare-earth complex materials as emitters. ©1998 American Institute of Physics.