Winter drainage of Laurel Creek Reservoir in southern Ontario exposed the benthic environment to atmospheric conditions for between 168 and 176 days. During the first 50 days, which had above-freezing temperatures, much of the fauna was destroyed. In the next 100 days the substrate became frozen to depths greater than 20 cm. Freezing of the substrate resulted in the loss of the oligochaetes, nematodes, and oribatoid mites as well as a large percentage of the chironomid fauna. Small numbers of the caddis fly, Agraylea multipunctata; the chironomid Cricotopus trifasciatus; and the molluscs Planorbula jenksii and Lymnaea palustris were found to survive the period of freezing and the subsequent short period of thawing before the refilling of the reservoir. Indirect evidence suggests the survival of small numbers of certain species of chironomids not found in the samples. Glyplotendipes barbipes showed the highest survival under the conditions of exposure, as the population immediately after refilling was between 12.5 and 46.4% of that found before drainage of the reservoir. The fauna did not actively move deeper into the substrate as freezing progressed although the probability of survival was greater at the deeper levels. A. multipunctata, C. trifasciatus, and G. barbipes have been found able to pupate and emerge after survival in the exposed substrate.