Several media were used t o enumerate bacteria in cultures of Desulforribrw uulgaria, the most suitable being a modification of Iron Sulphite Agar (Oxoid). This medium was also suitable for the enumeration of D. deaulfuricana and, with extra salt, D . aalexigena. Cultures of D. afrkanus and D. gigas were enumerated in a lactate-sulphateagar medium which gave higher counts than similar medio described in the literature. These media were suitable for counting the organisms in pure and mixed cultures. Neither of these media can be used successfully to enumerate D e~u~o~o~a e~Z~~ app.