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In this study, the water beetles of Amir Kalayeh and Anzali Marshes in northern Iran was investigated and compared. A total of 31 species of water beetles occurred in Amir Kalayeh Marsh. Of these 4 Dytiscid species were new recording for Iran,whilst 9 were new to Gilan province. The Hali— plid,Haliplus ruficollis is a new recording for Gilan. In addition 3 species of Hydrophilis are recorded from Iran for the first time. A total of 29 species of water beetles occurred in Anzali Marsh. Of these species, one species of Gyrinidae is new to Gilan whilst two species of Dytiscidae are new to the Iranian fauna. In comparison 24 species of water beetles are common to both Marshes, whereas 7 species are absent from Anzali Marsh and 5 species did not occur in Anir Kalayeh Marsh. In this investigation it was shown that the species diversity was much lower in Anzali Marsh but the number of species occurring was only slightly lower than in Amir Kalayeh Marsh.