A suite of six sterols, lanosterol, lanost-8(9)-en-3beta-ol, 4, 4-dimethylcholesta-8(14),24-dien-3beta-ol, 4, 4-dimethylcholest-8(14)-en-3beta-ol, 4-methylcholesta-8(14), 24-dien-3beta-ol and 4-methylcholest-8(14)-en-3beta-ol, were identified in the psychrophilic methanotrophic bacterium, Methylosphaera hansonii. Their presence suggests that the capacity for sterol biosynthesis in methanotrophic bacteria is limited to the family Methylococcaceae but which have widely different optimal growth temperatures.