The human CD30 gene, found on chromosome 1; 1p36, contains a microsatellite of the type [(CCAT)2-12CCACTTATGCAT]n within the promoter. As the microsatellite has been shown to be both polymorphic and involved in the transcriptional regulation of this gene, it is of potential interest with respect to interindividual differences in CD30 expression. Here we describe a method for determining length variation of this repeat region and determine the frequency and distribution of alleles of the CD30 microsatellite within the Western Australian population. As soluble CD30 levels are predictive for disease associated with human immunodeficiency virus (HIV)-1 infection, we also determined allele frequencies in an HIV+ cohort.