Egg production and egg survival of the American smelt, Osmerus mordax (Mitchill), were studied during the 1958 spawning run at Dean Brook, Ellsworth, Maine. The construction, number, and location of sampling units utilized in the estimate of egg production and egg survival are discussed. Egg production was 13,726,351 ± 3,525,971 and egg survival was 3,423,177 ± 610,384. Regressions of egg density and egg survival upon distance above the stream mouth are computed. An index of spawning activity could not be related to observed environmental variables. A density of smelt eggs for hypothetical maximum prolarval production was 11,745 eggs per square foot. Maximum prolarval production occurred in regions of moderate smelt egg deposition. Sources of egg mortality are noted and a nonstatistical estimate of prolarval production is presented: 75,440. A total egg mortality of 99.5 percent is indicated.