Malathion, ULV was applied from truck-mounted dispensers to 2 residential areas of Decatur, Illinois on 3 nights during the summer of 1977. The natural population of gravid Culex pipiens and Cx. restuans females was monitored using artificial oviposition sites in both treated and similar untreated areas. Results indicated about a 50% reduction in the number of egg rafts deposited in the treated areas on the night of an application. On subsequent nights, the difference between the number of egg rafts deposited in treated and untreated areas was not statistically significant.