In many families with histories suggestive of BRCA1- or BRCA2-related disease, the proband is deceased. Reliable assessment of archived tissue blocks not amenable to full gene sequencing would be helpful. In this study, a polymerase chain reaction (PCR) assay using primers that bracket the BRCA mutation site and microfluidics-based detection of heteroduplex/amplicon size differences was developed to circumvent artifacts associated with low quality DNA from formalin-fixed paraffin-embedded (FFPE) tissue. Genomic DNA was extracted from 100 FFPE specimens from patients that had previously undergone BRCA gene sequence analysis on blood specimens. Conventional PCR amplification products were differentiated using the Agilent 2100 Bioanalyzer. One FFPE specimen failed to amplify the wild-type alleles for all three sites and was therefore called indeterminate. All 62 FFPE specimens with known Ashkenazi Jewish founder mutations had both the wild-type and the correct mutated allele amplified, including one specimen that failed to amplify the mutant allele in other real-time PCR assays. Appropriately, 21 FFPE specimens known to have other BRCA1/2 mutations and 16 without any mutation had only the wild-type allele correctly amplified for each target. Therefore, by changing the primer location and detecting amplicons via heteroduplexes formed by size differences, we identified mutations from FFPE tissues missed using real-time methods.