Antiphospholipid antibodies (APL) are detected by both ELISA and tests for lupus anticoagulants (LA). We evaluated ELISA tests for IgG, IgM, and IgA isotopes of antibodies binding cardiolipin (CL) and phosphatidylserine (PS) in samples from LA patients presenting with recurrent miscarriages. All values were expressed in multiples of the normal median (MOM). In 32% (11/34) of cases, not only were all ELISA values at or below 2.5 MOM, but the distribution of these ELISA MOM values within the normal range was similar to distribution of values from LA negative controls with the same history. Neither the use of PS as the antigen nor the addition of IgA assays improved the correlation of ELISA results with the presence of LA. ELISAs are inadequate as the sole screening test for these separate, but often associated, families of APL.