Using　the　method　of　Ding　et　al.　[Int.　J.　Solids　Struct.　34　(1997)　3041],　the　fundamental　solutions　for　three-dimensional　two-phase　transversely　isotropic　piezoelectric　media　are　re-derived.　Based　on　the　fundamental　solutions,　the　displacements　and　the　electric　potential　at　any　point　for　an　internal　crack　parallel　to　the　interface　in　a　two-phase　transversely　isotropic　piezoelectric　medium　are　expressed　in　terms　of　the　displacement　and　electric　potential　discontinuities　across　the　crack　surfaces.　The　hyper-singular　boundary　integral-differential　equations　of　the　displacement　and　electric　potential　discontinuities　are　obtained　for　arbitrarily　shaped　planar　interfacial　cracks　in　three-dimensional　two-phase　transversely　isotropic　piezoelectric　media.　A　boundary　element　formulation　to　solve　the　boundary　integral-differential　equations　is　presented.　Numerical　results　of　stress　and　electric　displacement　intensity　factors　and　energy　release　rate　of　penny　shaped　and　elliptical　cracks　are　presented　to　illustrate　the　application,　accuracy　and　efficiency　of　the　proposed　method　in　analyzing　interfacial　cracks　in　three-dimensional　transversely　isotropic　piezoelectric　bimaterials.　(C)　2003　Elsevier　Ltd.　All　rights　reserved.