The bacterial chromatophores prepared from R. rubrum was immobilized by polyacrylamide entrapment to provide an efficient photosynthetic reactor for the generation of ATP and the reducing powers. The optimum yield of the immobilized chromatophores was obtained at the monomer concentration of 7.5% with its one-tenth amount of the crossfinking agent, The stability of chromatophores was improved markedly by the immobilization. The immobilized chromatophores showed the broad pH and temperature optimum at the pH range of 6.0 to 8.0 and at $40{sim}45^{circ}C$, respectively, The temperature dependent deactivation constants for the native and immobilized chromatophores were estimated to be about $3.5{ imes}10^{-2}$ and $8.7{ imes}10^{-3}$ per min, respectively, at $40^{circ}C$. By immobilization, the original chromatophore activities including photophosphorylation of ADP and photoreduction of $NAD^+$ were increased markedly and the operational stability was also improved. The $K_m$ values of the photophosphorylation by the immobilized chromatophores were estimated to be $4.6{ imes}10^{-4}M$ and $2.7{ imes}10^{-3}M$ for ADP and inorganic phosphate, respectively, which were about 15 to 30 times higher than those for the native chromatophores, In addition, in the case of the succinatelinked photoreduction of $NAD^+$, the immobilization of chromatophores resulted in a marked stimulation, especially by the presence of KCN and oligomycin. Several other properties related to the photochemical reactions mediated by the immobilized chromatophores were also studied and compared with those of the native chromatophores.