At this investigation Desulfovibrio was cultured in a chemostate with sulphate as limiting factor and pyruvate as C-source. From the ratio between the consumption of pyruvate and the consumption of sulphate it appears that with increasing D a shift takes place from fermentation to anaerobic respiration until D reaches a value of about 0,1. Then the ratio between fermentation and anaerobic respiration appears to remain constant until D reaches a value of 0,3. With further increasing D a suppression takes place of anaerobic respiration. At an experiment with a surplus of sulphate in the medium the measure of anaerobic respiration remained constant in the investigated interval from D = 0,02 till D= 0,28.