The incidence and diversity of methanogens in Priest Pot, a dynamic and active lake, were monitored by analysing mcrA gene sequences generated from total DNA samples obtained at different times of the year and amplified using the polymerase chain reaction. A number of mcrA clones were analysed by developing an RFLP-based protocol to generate a number of restriction patterns that were assigned to a number of classes. The RFLP patterns for each class were compared with published sequence information for mcrA from cultured methanogens as well as with those from other experimental studies. They could be used to assign tentative identification for some of the Priest Pot clones and also revealed the presence of a number of clones that could not be affiliated to any known methanogens. The limitations of using RFLP profiles of mcrA gene sequences for studying methanogen ecology are discussed.