To improve global budgets of the greenhouse gas methane, we studied methane consumption in sea-ice-covered Arctic seawater. The microbes using methane were present in abundances < 1 % in the seawater and sea ice. They consumed methane at rates increasing with increasing methane concentrations. In addition, differences in the methane concentrations and in the types of microbes between the ice and water indicate different microbial or physical processes in the two environments.