Two artificial oviposition sites containing aged alfalfa pellet infusion were exposed to natural populations of Culex quinquefasciatus in San Antonio, Texas, for 3 years. Numbers of egg rafts were counted daily and compared to weather data from a nearby station. Egg rafts were generally most numerous in summer months, declining in fall and increasing in spring. Oviposition occurred in winter only when temperatures were high enough. A particularly severe winter in 1983-84 reduced winter activity, but was followed by a great increase in oviposition in late spring. In summer, increases of oviposition were correlated with rainfall 2 to 3 weeks before the time of oviposition. Rainfall at the time of oviposition appeared to decrease oviposition. On a seasonal basis, lack of rainfall in the summer of 1984 was correlated with a decrease in oviposition.