Mosquito collections made on Saipan during September-October 1991, as part of a retrospective investigation of a Japanese encephalitis (JE) outbreak, are summarized. Forty-two larval habitats were sampled at 21 different sites. Most larvae were individually link-reared to the adult stage. Nine species, representing three genera and five subgenera, were collected. Numerous specimens of Culex tritaeniorhynchus, an established JE vector, were collected. Data on larval habitats including physical-chemical parameters and species associations are presented.