In the laboratory, newly hatched fry of Rivulus marmoratus were effective predators on 1st-instar Aedes taeniorhynchus. Adult fish consumed 4th-instar Ae. taeniorhynchus and egg rafts of Culex quinquefasciatus at a rate increasing with standard length of the fish. Predation of Rivulus marmoratus on Ae. taeniorhynchus larvae in the field was documented by observing the passage of larval/pupal remains through the gut. Laboratory reared fish released at known Ae. taeniorhynchus breeding sites survived over 1.5 years, but did not reproduce.