Existence of the P_<ASTEUR> effect in the respiratory mechanism of the infected root tissue of the club-root of Chinese cabbage was investigated by means of the W_<ARBURG>'s manometric technique. P_<ASTEUR> effect was existent effectively 〔(Q^<N_2>_<CO_2>×3/Q^<Air>_<CO_2>)>1〕 in the healthy root tissue and also in the hypertrophic fresh tissue of young stage of the infected root, while the effect disappeared (The ratio being <1) in the older stage of the diseased root tissue.