DNA samples from unrelated Alabama blacks with no family history of cystic fibrosis (CF) were analyzed with DNA markers linked to cf. Allelic frequencies of genetic markers detected by probes pmetH, pmetD, XV2c, KM19, and pJ3.11 were compared to those of other populations. Allelic frequencies for pJ3.11, XV2c, and KM19 in Alabama blacks and previously studied Caucasian populations were similar. In contrast, the met locus allelic frequencies in Alabama blacks were markedly different from those in Caucasian populations.