Distribution of heavy metals in the river-bottom mud was studied in River Usui flowing waste water of refinery drainage. The water and mud samples were collected in March and May 1972. Dryed soil was decomposed with HNO3 and H2O2, extracted with methyl isobutyl ketone, and the heavy metals were analyzed using atomic absorption. The samples obtained from the points near Takasaki city, flowing waste water from the refinery drainage, showed the highest concentration of Zn, Cd, Pb and Cu. The concentration of heavy metals in mud collected at about 300m down-stream from the inflow of drainage was lower. At the point where refinery drainage had been flowing in for along period, the amount of metals increased in proportion to depth, while at the point where waste water of drainage flowed in recent years, the concentration decreased in proportion to depth. There was a relationship among Cd, Pb, Cu and Zn in the surface layer of mud.