Currently the number of pregnant women who have indications for, but do not receive, prenatal cytogenetic diagnosis is increasing. The purpose of this study was to review the prenatal cytogenetic services and to analyze the effect of genetic counseling on performance of the prenatal cytogenetic test. From January 1987 to July 1988, there were 2,796 deliveries at Severance Hospital, Yonsei Medical Center, of which 126 patients had indications for prenatal cytogenetic diagnosis. Chromosomal abnormalities were found in 5 patients (1, monosomy X; 1, trisomy 18; and 3, trisomy 21). Four patients were found in the group who had indications for prenatal cytogenetic diagnosis while only one was found in the group who did not (p less than 0.01). The most common indication for prenatal cytogenetic diagnosis was advanced maternal age (59%). The prenatal test rate was highest in patients whose indications were a previous child with chromosomal abnormality (100%) and parental translocation carrier (100%). Most (89%) of the patients were tested by amniocentesis between the 16th and 20th week of gestation. The two most common reasons for patients not receiving a prenatal cytogenetic diagnosis were late registration (41%) and absence of genetic counseling (34%).