In Thailand, ceramic jars (135-200 liters) covered by aluminum lids commonly are used to store water for household use. In laboratory cages, gravid female Aedes aegypti (L.) were able to enter and oviposit in a covered water jar. Although the aluminum lid was not a complete barrier to gravid females, it reduced the number of eggs oviposited by 77%. A vertically oriented foam rubber ring which was compressed between the lip of the jar and the flange of the lid effectively sealed the jar against ovipositing mosquitoes.