Twenty to thirty percent of patients with atopic dermatitis (AD) are positive for antinuclear antibodies (ANAs). In this study we investigated the prevalence of ANA in 100 patients with AD and examined the difference between ANA-positive (ANA (+)) and ANA-negative (ANA (-)) patients with AD. ANAs were identified with indirect immunofluorescence on Hep-2 cells. Nineteen patients (19%) with AD were found to be positive for ANAs at titers ranging from 1 : 40 to 1 : 640. The rate of ANA positivity in male patients (20.4%) was higher than that in female patients (17.6%). The rate of ANA positivity differed significantly between patients with AD and healthy control subjects (p=0.0001, odds ratio: 2.8). There was also a relationship between ANA (+) AD and photosensitivity in male subjects (p=0.0346). The ANA (+) patients with AD showed higher levels of cedar pollen-specific IgE than did ANA (-) patients (p=0.0232). In ANA (+) patients disease severity was correlated with basophil counts (r=0.513, p=0.0344) and serum LDH levels (r=0.741, p=0.0056). The results indicate that patients with AD who are positive for ANA are a subpopulation of patients with AD.