Objective: The purpose of this investigation is to determine the frequency of chromosomal or genetic causes of recurrent spontaneous abortion. Methods: A cytogenetic study was made in of 921 couples for 13 years from January 1984 to December 1997 in which the woman was ascertained to have had two or more spontaneous abortions at our Cytogenetic Laboratory, Institute of Reproductive Medicine and Population, Seoul National University. Results: The overall incidence of chromosome anomaly was 80 out of 921 (8.7%). There were 34 cases (3.69%) of reciprocal balanced translocation and 13 cases (1.41%) of Robertsonian translocation. Also 17 cases (1.85%) of inversion and 5 cases (0.54%) of X chromosome mosiacism was observed. In the case of reciprocal balanced translocation, chromosome 8,6,7,13 were preferentially involved over others. And in the case of Robertsonian translocation, chromosome 13 was preferentially involved. Conclusion: Our study demonstrates that cytogenetic analysis is indicated in couples with 2 or more spontaneous abortion and about half of these disorders are reciprocal balanced or Robertsonian translocations.