A laboratory experiment using 12 cohorts of Aedes vexans was used to determine the preferred substrate moisture for ovipositing females. Two substrates were used: cheesecloth and sand. On both substrates the extremes (0% and 100% saturation content) were avoided. On cheesecloth, the preferred moisture level was 20% with a decline in preference as the moisture level increased. On sand, there was no clear optimal moisture. Sand moistures between 20 and 80% saturation content were equally preferred. Speculation for a difference in the moisture preference regimes on 2 substrates is included.