Eleven fungicides were examined for their effect on the growth and anabolism of Rhizobium sp. in pure culture. Of these, only 4 were found to inhibit growth of rhizobia at a concentration as low as 10 micrograms/ml. Growth inhibition by these fungicides appeared to be primarily due to inhibition of respiration, although thiophanate and anilazine also affected DNA and RNA synthesis, respectively. Inhibition is, however, transitory and the bacterium has the ability to overcome this initial inhibition without mutation.