The production of bacteriochlorophyll in anaerobic light and dark cultures is strongly inhibited by 2,6-dichlorophenol-indophenol sodium, 4-amino-2-methyl-1-naphthol-hydrochloride and methylene blue. Photophosphorylation is demonstrable 45 min after the start of bacteriochlorophyll synthesis. The induction of bateriochlorophyll synthesis is suppressed by mitomycin if the inhibitor is added together with the process of lowering the oxygen partial pressure. The effect of puromycin is also dependent on the time of addition. Mitomycin and puromycin have no influence on the production of coproporphyrin. In the presence of mitomycin or puromycin and δ-aminolevulinic acid the synthesis of porphyrin is intensely increased but the synthesis of bacteriochlorophyll is blocked. These and other results are interpreted as indicating that control over bacteriochlorophyll synthesis occurs by a gene dependent regulation fo the biosynthesis of those enzymes which are responsible for the production of bacteriochlorophyll from protoporphyrin.