The oral cavities of 200 consecutive psoriasis patients, most of them with widespread disease on the skin, were examined (man/woman ratio 1.63:1, mean age of the patients 43.7 yr). The average duration of the disease at time of examination was 15.8 yr. When questioned, 16% of the patients reported changes in the joints, which, according to them, had been verified by radiography. 72.5% of the patients reported on nail involvement at some time during their disease. Fissured tongue was present in 9.5% of the patients, and geographic tongue and smooth tongue each in 1% of the patients. Angular cheilitis was found in 3.5% of the patients. In 20 out of 200 cases, the oral mucosa showed changes and biopsy was taken. Four out of 20 patients showed histologic features typical of psoriasis, including accumulations of leukocytes in the upper layers of the epithelium, all with widespread psoriasis skin involvement. Areas of oral mucosa were most often deep red in color, the buccal mucosa and tongue being the two most common sites. Two out of these four patients had a fissured tongue and one had a geographic tongue.