Cytogenetic records were examined from consecutive nononcology blood specimens from 2,821 patients referred for cytogenetic services to Vanderbilt University Medical Center, Nashville, Tenn, from January 1985 to December 1992. We grouped the records according to reasons for referral and diagnoses. The most common reasons for referral were history of multiple abortions/miscarriages (23.3%), possibility of chromosomal abnormality (18.8%), and possible presence of the fragile X syndrome (15.6%). Overall, 2,418 (85.7%) patients were found to have normal chromosomes, and 403 (14.3%) patients were diagnosed with a cytogenetic abnormality. For example, 20 (5.4%) of the 373 males referred for the fragile X syndrome, or 1.4% of all males (20 of 1,428) excluding those with ambiguous genitalia, were diagnosed with this syndrome while 8 (2.1%) of the 373 males had a chromosome abnormality other than the fragile X chromosome. In addition, 85 (70.2%) of 121 males referred for Down syndrome had this syndrome, and only 53 (40.8%) of 130 females referred for Down syndrome had this diagnosis. This study should assist physicians in middle Tennessee and surrounding areas by increasing their awareness of the types and frequencies of cytogenetic diseases and by providing figures for comparison with other regions of the country.