To determine the life cycle and demographic characteristics of the inconnu, Stenodus leucichthys, and burbot, Lota lota in the Slave River, Northwest Territories, we sampled between June and December, 1994. Inconnu are migratory utilizing the Slave River for spawning. They were most abundant in the river in late September and October. Based upon thegonadosomaticindex, inconnuprobablyspawninmid-tolate-OctoberintheSlaveRiver. Burbot appear to be highly sedentary in the open water season because few were caught until December under ice cover. Inconnu had faster growth rates and earlier age-at-maturity ( ages 5-7 for males and 7-9 for females) than more northerly inconnu populations. In contrast, burbot matured later (age 5) and grew more slowly than other populations. Inconnu mean fecundity-at-age was between 108,086 to 124,493 eggs per female. Based on the demographics of the two species in the Slave River, inconnu would be more vulnerable to environmental change.