During 1995-2000, mosquitoes were collected from sites throughout Rhode Island and testedfor the presence of arboviruses. Mosquito trapping was done weekly from June to October with CO2-baited lighttraps. In all, 186,537 mosquitoes belonging to 7 different genera were collected, of which Coquillettidia perturbanswas most abundant. A total of 6,434 pools were processed for arbovirus isolation, from which 193arboviral isolations were made. These included 109 Highlands J, 71 eastem equine encephalomyelitis, 1 Californiaencephalitis serogroup, 2 Jamestown Canyon, 3 Cache Valley, and 9 Flanders viruses. Our isolations ofFlanders virus represent the lst reported occurrence of this virus in Rhode Island. After the 1999 suddenoccurrence of the West Nile virus (WN) in the New York City area, a dead-bird surveillance proglam was startedto test for this virus. Although no isolations of WN were made from mosquitoes, 87 virus isolations were madefrom a total of 330 wild birds tested. All the WN-infected birds were either American crows or blue jays.Isolation of WN from dead birds marked the lst documented appearance of this virus in Rhode Island. Significantinterannual variation of arbovirus activity in Rhode Island prompted us to examine if climate-associated factorssuch as rainfall and temperature correlate with virus activity. Total rainfall amounts from May to June werehigher than normal in 1996 and 1998. These years showed significantly higher arbovirus activity. Deviationsfrom normal temperature showed low correlation with arbovirus activity during the 6-year study period. Therefore,precipitation appeared to be more important than temperature in predicting arbovirus activity in RhodeIsland.