Validity of the laser flare-cell meter in uveitis was evaluated. A comparative study of slit-lamp examination and flare-cell meter measurements was carried out in the evaluation of iridocyclitis in a total of 251 measurements in patients with uveitis of various etiologies, including Behçet's disease, Vogt-Koyanagi-Harada's disease and sarcoidosis. The data obtained by these two methods showed a significant overall correlation both in the measurement of flare intensity (Kendall tau = 0.580, P less than 0.001) and cell count (tau = 0.390, P less than 0.001). Problems inherent to the slit-lamp examination were marked in terms of wide variations in grading within groups and large overlaps in scores between groups. The flare-cell meter was highly reliable in the measurement of flare intensity; whereas it could not detect low numbers of cells in some cases. Ninety-one eyes of patients with Behçet's disease were divided into three groups based on the interval from the last ocular attack episode. The flare-cell meter examination revealed that values for flare intensity remained abnormally high even in patients free from an attack episode for more than six months prior to the examination. It was considered that deterioration or breakdown of the blood-aqueous barrier function persists in patients with Behçet's disease.