Because of their relative unimportance to recreational hunters, almost nothing is known about the population dynamics of waterfowl in the tribe Mergini in North America. Species-specific annual survival estimates are important to ecologists and managers both for understanding the evolution of life histories and for implementation of management plans. Using capture-recapture methodology, we estimated annual survival of female Hooded Mergansers breeding in man-made nest boxes in southeast Missouri from 1987 - 1995. Survival averaged 0.74 + 0.045 (95% confidence limits - 0.652 - 0.828), and analysis suggested lower annual survival in two years. Annual survival was not correlated with composite winter temperature or total rainfall variables for the Mississippi Alluvial Valley. Mean survival was higher than for female Wood Ducks using the same population of boxes during the same years. Results are consistent with the characterization of sea ducks as long-lived relative to dabbling ducks. Annual differences in survival suggested here emphasize the need for research identifying both the timing and sources of Hooded Merganser mortality.