Objective:To investigate the changes of interleukin(IL)-4 and IL-12 following active immunotherapy of women with unexplained habitual abortion(UHA) .Metbods:The expression of IL-4 and IL-12 mRNA was measured by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) in peripheral blood mononuclear cells(PMBC) . The samples were taken from 30 non-pregnant(NNP) women and 30 UHA women before and three weeks after active immunotherapy.Results: (1)IL-4 mRNA expression was lower significantly ( P