A　hybrid　implicit-explicit　FDTD　(HIE-FDTD)　algorithm　is　proposed　in　this　paper.　In　the　HIE-FDTD　algorithm,　semi-implicit-and　explicit-difference　schemes　are　imposed　on　two　different　field　components,　respectively　and　the　field　component　with　implicit　difference　is　updated　by,　solving　simple　tridiagonal　matrix　equations.　The　HIE-FDTD　method,　although　conditionally　stable,　allows　for　larger　time-step　Size　than　the　conventional　FDTD　method　because　the　stability,　condition　of　the　HIE-FDTD　method　is　weaker　than　that　of　the　conventional　Yee＇s　FDTD　algorithm.　The　demonstrated　numerical　dispersion　relation　of　the　HIE-FDTD　method　is　found　to　be　identical　to　that　of　the　of　the　HIE-FDTD　are　verified　by　method.　The　accuracy　and　efficiency　numerical　simulation　results.　(C)　2003　Wiley　Periodicals,　Inc.