Limnological data collected during a four and one-half year period at Lake Sinclair is reviewed. Comparison of temperature and oxygen profiles are made in areas of the lake receiving hot water discharge and in unaffected areas. Hot water discharge was found to increase temperature and dissolved oxygen substantially during both summer and winter. In addition, hot effluent eliminated or altered the thermocline in the affected area. These effects were evident in varying degrees for 2.3 miles below the source. Observations concerning the sport fishery within the area receiving hot water discharge are noted. The possible effects of hot water discharge on the habitat and an aquatic ecosystem is also discussed.