It was demonstrared in this report that mucoprotein from human serum and bile interferes only to a slight degree with the precipitin reaction between human bile and anti human whole serum rabbit sera (anti W.S.).This dose not seriously affect our original procedures described in a previous report for detecting the presence of albuminocholia,that is,tha coaulable protein in the bile.A correction may be applied with anti human serum mucoprotein rabbit sera (anti M.P.)for more precise determination.