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A clinical and immunologic evaluation of a direct agglutination test for pregnancy∗∗DAP test, Wampole Labs., Stamford, Connecticut.was performed on sera from 303 pregnancies, and a correctly positive result was obtained in 96 per cent. Prozoning accounted for 3 of the 4 false negative test results as well as for many of the weaker but correct positive results and was related to sampling during the periods of peak human chorionic gonadotropin (HCG) production (fiftieth to ninetieth day). A parallel control study of 200 sera from nonpregnant women yielded 7 (3.5 per cent) false positive and 9 (4.5 per cent) inconclusive test results. Three hundred and thirty-nine sera from a selected group of patients with immunologic disorders gave 19.2 per cent (55/339) inconclusive and 7.3 per cent (25/339) false positive results. There were indications that many of the inconclusive test results were due to circulating macroglobulins. A recently added control reagent detected these proteins in many cases.