Hydrogen production from the wastewater of tofu factory was examined by using anoxygenic phototrophic bacterium Rhodobacter sphaeroides immobilized in agar gels. The maximum rate of hydrogen production observed from the wastewater was 2.1 1 h(-1) m(2) gel which was even slightly higher than that from a glucose medium (as control). The hydrogen production lasted up to 50 h. The yield of hydrogen was 1.9 ml/ml wastewater or 0.24 ml/mg carbohydrates contained in the wastewater. This yield corresponds to 53% or 65% of that from the glucose medium, according to the different expressions of the yield. The TOC (total organic carbon) removal ratio in 85 h reached 41% which was comparable to that from the glucose medium. The immobilization protected the bacterium from the inhibitory effect of ammonium ion.