A laboratory experiment was conducted using machine stripped cotton to determine trash removal rates for four successive passes through a typical seed cotton cleaning unit consisting of an inclined cleaner and a stick extractor. The inclined cleaner was an air-fed machine containing six cleaning cylinders and 3/8-in. dia. grids. The stick extractor was a conventional gravity-fed machine containing two 18-in. dia. saw cylinders. Six test cottons representing a broad range of initial trash and moisture contents were processed through the 6-foot wide cleaning unit at rates of approximately 150, 250, and 350 pounds of clean seed cotton per minute. Seed cotton samples were collected before and after each pass through the cleaning unit for determination of bur, stick and fine trash content by conventional fractionation procedures, and for determination of moisture content by the oven method. Multiple linear regression techniques were utilized to develop prediction equations for output bur, stick, and fine trash contents as functions of input trash and moisture levels, feed rate, fiber staple length, and fiber micronaire value. These analyses resulted in the following prediction equations which describe the performance of the cleaning unit over a wide range of operating conditions: