Background: Recurrent abortion is defined as three or more consecutive pregnancy losses. We aimed to determine the relationship between male sperm parameters and hypo-osmotic swelling score and recurrent abortion. We also studied whether washing of spermatozoa and intrauterine insemination in patients with recurrent miscarriage and low score hypo-osmotic swelling test in male partners could improve the outcome of pregnancy. Methods: Between February 2003 and September 2006 in gynecology clinics affiliated to Shiraz University of Medical Sciences, 176 women with a history of recurrent abortion and their male partners were selected as study group. And 159 healthy and fertile couples without a history of recurrent abortion were selected as control group. The relationship between male sperm parameters and hypo-osmotic swelling test and recurrent spontaneous abortion in their female partners was evaluated after intrauterine insemination for those with abnormal hypo-osmotic swelling test. Outcome of pregnancy in patients with recurrent abortion whose male partners had low score hypo-osmotic swelling test was evaluated after intrauterine insemination. Results: Low scores of hypo-osmotic swelling test were more frequently seen in the study group than the controls: 116 (65%) versus 24 (15%). The mean hypo-osmotic swelling score was significantly lower in the study group (P< 0.001). The outcome of pregnancy improved after intrauterine insemination in those with low score hypo-osmotic swelling test. The pregnancy success rate in the treated group (pregnant with intrauterine insemination) was 77.77% while in the untreated group (pregnant without intrauterine insemination) was 30.76% with a success rate ratio of 2.04. Conclusion: There was a positive relationship between low hypo-osmotic swelling test score in male partners and recurrent abortion in their wives. Intrauterine insemination improved the outcome of pregnancy in these couples.