Loss-of-function mutations in the gene encoding filaggrin (FLG) can cause the semidominant keratinizing disorder ichthyosis vulgaris (OMIM 146700). To identify FLG mutations in three Chinese pedigrees with ichthyosis vulgaris, we sequenced the entire coding region of FLG in the proband of each pedigree. We found two novel FLG null mutations (c.477-478insA and c.6218-6219delAA) and a known mutation (c.3321delA). Both novel mutations were identified in the proband of pedigree 1; c.477-478insA was inherited from the proband’s father, and the other was a de novo mutation. Neither of these two mutations was found in 200 unrelated controls. These findings extend the spectrum of functional FLG variants possibly causing ichthyosis vulgaris. Interestingly, the proband of pedigree 1 was compound heterozygous for these mutations, but had a mild phenotype, suggesting that an incomplete penetrance factor and perhaps other unknown factors may be involved in the pathogenesis of ichthyosis vulgaris.