Abstract: Recurrent spontaneous abortion and fetal loss are common in obstetrics and gynecology (60% of pregnancy loss). Immunological factor suspected to have a major role in These problem. Receent studies suggest association of antiphospholipid antibodies, especially anticardiolipin antibodies (aCL) with recurrent pregnancy loss. Different studies report different association (5-51%), we determine the prevalence af aCL in recurrent, pregnancy loss in Sari during 2000-2003. In a descreptive study women with a history of at least two pregnancy loss without any known etiology like hormonal Imbalance, systemic hypertention, diabet, infection, hyperthyroidism and, anatomical abnormality in genital tract were studied. 512 case, for presense of aCL in serum were investigated. The patient sera were tested by Enzyme Linked Immunosorbant Assay (ELISA) method. Commercial standard ELISA kit from GENESIS company were used, According the kit procedure, 5 to 11 U mL^-1, 11 to 13 U mL^-1 and >13 U mL^-1 results of measurement were, respectively consider as the negative (normal), borderline and positive values. The prevalence of aCL determined and Confidence interval (CF) were estimated. 512 women with age range of 18-40 (28.02�5.66) were studied. aCL wase detected in sera of 57 (11.1%) cases, with confideuce interval of 2.7 (11.1�2.7) 447 (87/4%) cases were negative for aCL and in 8 (1.5%) were intermediate. 49.1 of pregnancy loss with positive aCL were in first trimester of pregnancy and 50.9 in second and third timester with odd`s ratiuo of 3.1. The prevalence of aCL in recurrent abortion and fetal loss in sari are not high and it is higher in second and third timerster.