Homozygosity for a novel hemochromatosis (HFE) gene splice site mutation (IVS5+1 G/A) was previously reported in a 48-year-old Vietnamese man residing in Germany who had an elevated serum ferritin (SF) and transferrin saturation (TS) and severe iron overload on liver biopsy. This mutation was not found in 222 controls of central European origin but has been found in Southeast Asians living in Vietnam without evidence of iron overload. Hemochromatosis and iron overload screening (HEIRS) Study is an ongoing, multiethnic, primary care-based study of 101,168 North American adults, including 12,772 Asians, a group that the HEIRS Study found has a significantly higher than expected prevalence of elevated serum TS and SF but very low prevalence of the common C282Y and H63D HFE alleles usually associated with hereditary hemochromatosis. It was hypothesized that the IVS5+1 G/A splice site mutation might explain some elevated biochemical iron measures in North American Asians. Overall, 200 Vietnamese subjects from the Los Angeles Field Center who had TS and SF values greater than the 75th percentile of all HEIRS Study participants after adjusting for covariates and 149 controls randomly selected to represent this Vietnamese population were genotyped. Among cases, 1 homozygous mutant and 7 heterozygotes were found; among controls, 1 homozygous mutant and 4 heterozygotes were found yielding an allele frequency of 2.32% for cases and 2.04% for controls (P>0.5). This finding suggests that the HFE IVS5+1 G/A splice site mutation is not the major explanation for unexpectedly high prevalence of TS and SF in North American Asians.