Let　script　capital　U　sign+(2k)　be　the　set　of　all　unicyclic　graphs　on　2k(k　≥　2)　vertices　with　perfect　matchings.　Let　U12k　be　the　graph　on　2k　vertices　obtained　from　C3　by　attaching　a　pendant　edge　and　k-2　paths　of　length　2　at　one　vertex　of　C3;　Let　U22k　be　the　graph　on　2k　vertices　obtained　from　C3　by　adding　a　pendant　edge　at　each　vertex　together　with　k-3　paths　of　length　2　at　one　of　three　vertices.　In　this　paper,　we　prove　that　U12k　and　U22k　have　the　largest　and　the　second　largest　spectral　radius　among　the　graphs　in　script　capital　U　sign+(2k)when　k≠3.　©　2003　Elsevier　Science　Inc.　All　rights　reserved.