Objective: VonWillebrand disease (vWD) is the most common inherited bleeding disorder with a prevalence of about 1%. The vWD is a disese due to quantitative (type 2) and qualitative (type 1 and 3) defects of VonWillebrand factor (vWF). vWD inherited autosomally (Dominant or Recessive) depends on its type. vWF is a large glycoprotein involve in promoting platelets to damage site of endothelium and as a carrier of factor VIII in the circulation. type 3 vWD, is a rare but severe form of disease with nearly complete deficiency of vWF. It is transmitted as an autosomal recessive trait in homozygous or compound heterozygous. The mutation cause this type distribute over the entire VWF sequence. Exon 28 is the largest exon of this gene by length of 1.4 kb. Most of the reported mutation gather in this exon, though exon 28 is the first choice of all mutation detection study of vWD. Materials and Methods: Blood samples were collected from 32 patients from 23 families with the type 3 vWD. The genomic DNA was extracted by the Bioneer kit according to the manufacture instructions. Exon 28 was amplified by PCR and the PCR products were sequenced by the automated DNA sequencer (ABI Company). The detected nonsense mutation was confirmed by the self-made PCR-RFLP specific to detect the mutation at codon 1311, which causes a stop codon. Results: Sequencing results revealed a point mutation within exon 28, at codon 1311, with changes CAG to TAG, which results to a stop codon. Twenty eigh patients were heterozygous and the only one patient showed the mutation in the homozygous manner. This mutation has been previously reported in some other population. In addition some single nucleotde polymorphisms (SNP) were found in this exon that didn't documented in other world populations. Conlussion: This is the first organized molecular study of the vWD in Iran specially in the region Broad variety of mutation such as deletions, non-sense and missense mutations and defective mRNA expression have been described as the cause of quantitative deficiency of vWF. In this study, 1 patient had homozygous non-sense mutation, 28 patients were heterozygous for this mutation and 3 patients didn't have any mutation in this part of the gene. All the patients harboring the above mentioned mutation suffer the type 3 of the vWD disease. This mutation had been previously reported in ethnic groups. The results are significant for the reason of providing new insight to molecular diagnosis of vWD for further studies.