Although tree roots in sewers and drains cause losses of millions of dollars each year in the U. S., there has been very little research on control methods. This is a report of 2 1/2 years of chemical control tests in cooperation with the Sacramento County Department of Public Works. Two chemicals—metham (Vapam), and dichlobenil (Carsoron)—used alone, or in combination, killed roots in sewer pipes in one-hour-long treatments by soaking.