Tharae rate of methane released from the sediment‐water interface and from the surface of the water of Lake Wingra, Madison, Wisconsin, was measured during the summer months for 2 years. The amount of methane escaping the lake is estimated to be an important factor in the carbon budget of the lake. Most rapid methanogenesis was in shallow water (less than 1 m deep) and in the uppermost 5 cm of sediment. The numbers of methanogenic bacteria were estimated by a most probable number technique to vary from approximately 102to 3 × 104methanogens per gram of dry weight sediment during winter and summer, respectively.