Involved regions of the skin in atopic dermatitis (AD) patients have an altered barrier function. Whether uninvolved skin also has a diminished barrier is controversial. To assess the barrier function of uninvolved skin in AD patients, the percutaneous penetration of polyethylene glycols (PEGs) of various molecular sizes was determined in vivo in AD patients and control subjects using tape stripping of the stratum corneum (SC). The diffusion and partition coefficients were determined using Fick's second law of diffusion. The SC thickness was similar in both groups; however, the trans-epidermal water loss was higher in atopic skin. The apparent diffusion coefficient of PEGs through atopic skin was twice as high as through normal skin, and decreased with increasing molecular weight (MW) in both groups. The partition coefficient in the skin of AD patients was half of that for normal skin but as for normal skin, there was no MW dependency. Although atopic skin exhibited altered barrier with respect to diffusion and partitioning, the permeability coefficients were nearly the same for atopic and normal skin. The results support the assumption of altered skin barrier of AD patients even in the skin that is visibly unaffected by disease.