Herlitz junctional epidermolysis bullosa, a severe epidermal blistering disorder, is inherited in an autosomal recessive manner. It has recently been shown that, in kindreds with junctional epidermolysis bullosa, the disorder results from mutations in the gamma 2 chain of laminin-5, a basement membrane protein synthesized by the basal cells of stratifying squamous epithelia. In this report we describe a mutation identified in the beta 3 chain gene of laminin-5 in a family with Herlitz junctional epidermolysis bullosa. The disease is caused by a homozygous deletion of 1 bp that leads to a frameshift and premature termination codon. The segregation of the mutated allele in the family is consistent with the pathogenic role of the mutation. We also report a direct DNA-based prenatal exclusion of Herlitz junctional epidermolysis bullosa in a pregnancy at risk using a chorionic villus biopsy and allele-specific oligomer hybridization from polymerase chain reaction-amplified genomic DNA.