Although the contribution of sediment-generated methane to dissolved oxygen demand has been well documented in a number of stratified lakes throughout the world, little work on the subject has been performed in shallow, un-stratified lakes. To quantify the role of methane in carbon and oxygen cycling in such environments, carbon and methane budgets were prepared for Carlisle Lake, a small, shallow, unstratified, hypereutrophic lake. The budgets reveal that about 10 percent of the summer oxygen demand is exerted by the bacterial oxidation of methane. Methane production accounts for recycling of about 5 percent of the carbon produced by primary production and about 10 percent of the carbon reaching the sediments. Methanogenesis may indicate the degree of heterotrophic activity in sediments. This work supports such a conclusion and also suggests that methanogenesis may be indicative of the intensity of nutrient regeneration from sediments.