1. Ten Rh-negative sensitized pregnant women were treated with Rh hapten in doses of 100 to 600 mg. weekly for periods varying from seven to twenty-eight weeks antepartum.
2. Three patients with heterozygous husbands delivered Rh-negative infants. Maternal antibody titers were unaffected by hapten therapy.
3. Three patients delivered Rh-positive infants displaying varying degrees of erythroblastosis fetalis.
4. The pregnancies of 4 patients terminated with fetal deaths in utero despite hapten therapy.
5. There does not seem to be any evidence that Rh hapten in the doses and manner employed altered the course or outcome of any of the 10 pregnancies.
ACKNOWLEDGMENTS The authors wish to express their appreciation to the following physicians who referred patients for study: Drs. John M. Haws, Arthur Mandy, Isadore Scher, I. A. Siegel, John G. Morris, J.K.B.E. Seegar, Jr., Sidney Linas, M. G. Kappelman, and George C. Basil.