We have generated mutant mice for epidermal-type fatty acid binding protein by the gene targeting technique and examined the phenotype in detail. Despite a lack in the expression of epidermal-type fatty acid binding protein mRNA and its protein in the skin and other tissues of the mutant mice, the animals appeared normal in gross and histologic examination. Northern blot analysis of other fatty acid binding proteins revealed a distinct elevated gene expression of heart-type fatty acid binding protein in the skin of the homozygous mice. In analyses of the skin, no differences were observed in contents of major fatty acids, electron microscopic appearance as well as inflammatory responses in ear skin between the mutant and wild-type mice. Basal transepidermal water loss of homozygous mice was lower than that of the wild mice. When acetone was applied to the skin for disruption of the water permeability barrier, recovery in transepidermal water loss was delayed, although maximum transepidermal water loss upon acetone treatment was similar between homozygous and wild-type mice in terms of size and time course. The molecular mechanism by which epidermal-type fatty acid binding protein contributes to the water barrier function of the skin remains to be elucidated.