Clostridium pasteurianumfermented glucose to acetate, butyrate, CO2and H2. In batch cultures the fermentation pattern was only slightly affected by culture pH over the range 8·0 to 5·5. The acetate/butyrate ratio was always higher than or equal to one. Between 2·14 and 2·33 mol H2was produced per mol glucose fermented. At unregulated pH, more butanol and less butyrate was formed. In a carbon‐limited chemostat, the steady‐state acetate/butyrate ratio was always lower than one. H2production was approximately 1·70 mol per mol glucose consumed. Substantial amounts of extracellular protein were formed. With decreasing pH, acetate and formate production decreased, while H2production was highest at pH 6.0. With increasing dilution rate (D), the product spectrum hardly changed, but more biomass was formed.YglucosemaxandYATPmaxwere 55·97 and 31·48 g dry weight per mol glucose or ATP respectively. With increasing glucose input the formation of fatty acids and H2slightly decreased.Continuous cultures fermented mannitol to acetate, butyrate, butanol, CO2and H2. With acetate as co‐substrate, butanol production and molar growth yields,YmannitolandYATP, markedly decreased, while the butyrate and H2production increased. The latter reached a value of 2·21 mol H2per mol mann