Mutations in the interferon regulatory factor 6 (IRF6) gene are known to cause van der Woude syndrome (VWS), a common syndromic form of oro-facial clefting characterized by the familial occurrence of mixed clefting (cleft lip with or without a cleft palate and cleft palate alone in the same family) and lower lip pits. As lip pits are not present in all cases of VWS, IRF6 mutations can cause a phenotype identical to non-syndromic clefting. However, recent studies failed to identify IRF6 mutations in sporadic and familial non-syndromic clefting, concluding that testing for IRF6 was not warranted for sporadic or familial non-syndromic clefting. Here we report on two families that demonstrate familial mixed clefting in which mutations in IRF6 were identified, suggesting that IRF6 testing does have a role in familial, non-syndromic OFC. © 2010 Wiley-Liss, Inc..