Liquid media containing potato extract and 1% of glucose or sucrose were used to culture root-nodule bacteria (rhizobia) in shaken Erlenmeyer flasks. For comparison, these bacteria were also cultured in yeast extract-mannitol broth (YEMB) as a standard medium. Proliferation of rhizobia was monitored by measuring optical densities (OD₅₅₀) of the cultures and by plate counting of the viable cells (c.f.u) of the bacteria. In general, multiplication of the rhizobia in potato extract-glucose broth (PEGB) and potato extract-sucrose broth (PESB) was markedly faster, as indicated by higher values of OD₅₅₀, than in YEMB. The numbers of R. leguminosarum bv. vicae GGL and S.meliloti 330 in PEGB and PEGB were high and ranged from 1.2×10¹⁰ to 4.9×10¹⁰ mL⁻¹ after 48 h of incubation at 28°C. B. japonicum B3S culture in PEGB contained 6.4×10⁹ c.f.u. ml⁻¹ after 72 h of incubation. PEGB and YEMB cultures of the rhizobia were similar with respect to their beneficial effects on nodulation of the host-plants of these bacteria.