The objective of this study was to identify important risk factors for spontaneous abortion (SA) among Saudi women. It was a case-control study conducted at King Khalid University Hospital, Riyadh, Saudi Arabia. The cases were 226 consecutive women hospitalized for SA between October 1992 and January 1993. The controls were 226 consecutive women who had normal delivery in the same hospital during the same period. Bivariate analysis using chi-square tests and estimates of relative risks indicated a positive association of age at menarche with risk of SA (P < 0.01). Also, there was a significant higher risk of SA when a woman was married to a blood related husband than if married to a non relative (RR = 2.1). The number of previous abortions was also positively related to the risk of SA in the current pregnancy (P < 0.01). Compared to primigravidas, the risk of SA was 3.2 times greater than if the outcome of the most recent pregnancy was also an SA. Other factors that had significant bivariate association with SA were a family history of SA, abdominal trauma, and infection during pregnancy. When multiple logistic regression was used to adjust for the effects of confounding variables, all the factors that showed significant bivariate association with SA (except outcome of the last pregnancy) remained significant. Early menarche may be protective, but further study is needed to confirm this. Greater attention should be given to pregnant women who had personal or family history of SA and those who had trauma and/or infection during pregnancy. Premarital counselling concerning consanguineous marriages is recommended.