In this study, 16S rRNA gene primers were designed to complement the suite of already available PCR primers for the detection of different methanogens involved in biogas production through anaerobic digestion by SYBR Green real-time PCR. Primers designed for use in TaqMan real-time PCR for the organisms Methanosaeta, Methanosarcina, and Methanoculleus have been described previously; however, we found that (i) the Methanoculleus primers were not specific to members of the genus and that (ii) the Methanosarcina primers did not work specifically with SYBR Green real-time PCR. Thus, we designed new primers for these and other methanogens, and we optimized SYBR Green real-time PCR assays. Primers were tested by end-point and real-time PCR, and they were found to work specifically and sensitively. Application of these primers will allow the detection and quantification of Methanoculleus, Methanosarcina, Methanothermobacter, and a group of yet uncultured archaea from anaerobic habitats.