The prevalence of atopic dermatitis (AD) has increased substantially. Previous studies have focused mostly on pediatric patients, while epidemiological investigation on adult AD has been very limited. The aim of this study was to determine the prevalence and clinical features of adult AD in outpatients with dermatitis and eczema in China mainland. A multicenter cross-sectional study was conducted among outpatients with eczema or dermatitis from 39 tertiary hospitals of 15 provinces in China from July 1 to September 30, 2014. Of 8758 patients, 407 were adult AD. Compared with adults with other types of dermatitis, the mean age (41.8 +/- 14.3 vs 42.04 +/- 15.38 years, P < 0.05) and onset age (35.2 +/- 11.2 vs 39.2 +/- 14.0 years, P < 0.001) of adult AD were younger, and mean disease duration was longer (5.3 +/- 7.1 vs 2.8 +/- 4.9 years, P < 0.001). About 53.3% adult AD involved 3 or more body locations, higher than adults with other types of dermatitis (34.4%, P < 0.001), but lower than those with pediatric and adolescent AD (73.8%, P < 0.001). History of asthma (19.2% vs 6.9%, P < 0.001) or allergic conjunctivitis (21.9% vs 14.9%, P < 0.05) was more common in adult AD than pediatric/ adolescent AD. Suspected bacterial infection was more frequently in adult AD than adults with other types of dermatitis (24.3% vs 14.6%, P < 0.001) and pediatric/ adolescent AD (24.3% vs 14.9%, P < 0.001). More severe itching was observed in 31.4% of adult AD, higher than that of adults with other types of dermatitis (15.4%, P0.05). The highest (8.7%) and lowest prevalence (3.7%) of adult AD were in 25 degrees N to 30 degrees N and 35 degrees N to 40 degrees N latitude region. A substantial part of adult outpatients with eczema or dermatitis is adult AD. Middle age, more body location involvement, more suspected bacterial infection, and severe itching are the main clinical feathers of adult AD. Geographical environment and economic situation work in synergy to adult AD.