Three variants of human interferon (IFN)-alpha 8a gene, that is, IFN-alpha 8b, and IFN-alpha 8c, have been reported previously. They differ from each other by changes in their coding region at nucleotide positions 359-360, 372, and 550. Human genomic DNA obtained from over 28,000 healthy blood donors and from 4 human cell lines was used in the polymerase chain reaction (PCR) designed for specific amplification of the IFN-alpha 8 gene fragments. The resulting PCR product was analyzed by (1) restriction endonuclease digestion, (2) DNA sequencing, and (3) allele-specific secondary PCR amplification. Only one sequence for IFN-alpha 8 was identified, and that was for IFN-alpha 8b. The sequences for IFN-alpha 8a and IFN-alpha 8c were not detected after PCR amplification either in the pooled leukocytes obtained from > 28,000 individuals or in cell lines tested. These data suggest that the naturally occurring variant or allele for IFN-alpha 8 in the population is IFN-alpha 8b. IFN-alpha 8a and IFN-alpha 8c variants were consistently below the level of detection of the assays and, if present at all in the population, are very rare.