The inheritance of light dependence for conidial development in Bipolaris oryzae was analyzed using single-ascospore isolates. When a photo-induced strain was crossed with another photo-induced strain, only photo-induced progeny were produced. When a photo-induced strain was crossed with a non-photo-induced (I) strain, photo-induced and nonphoto- induced (I) progeny were produced in a ratio of 1 : 1. However, when a photo-induced strain was crossed with a non-photo-induced (11) strain, a non-photo-induced (I) progeny were formed in addition to parental types. It was suggested that genes for photo-control of conidiophore induction and genes for photo-control of conidiophore maturation are located on the same chromosome.