Serum levels of human placental lactogen were measured by hemagglutination inhibition reaction in 26 normal pregnant state and in patients with 16 toxemia and 6 F.D.I.U. beyond their thirtieth week of gestation to evaluate their clinical usefulness. It was realized that HPL-HAIR Test Kit was easy to use and produced reliable results. The general conclusion were as follows: 1) HPL value was $6{sim}8$ug/ml in normal pregnancy. 2) The levels in mild toxemia were similar in the normal state. 3) The levels in severe toxemia were similar or slightly lower than in the normal and mild toxemia. 4) The levels in F.D.I.U. were lower than in the normal state.