The authors report the experience of applying immunocytochemistry in routine cytological examination and its contribution for diagnosis during a period of 3 yr in Veterans General Hospital-Taipei, Taiwan. From August 1991 to July 1994, the cytology laboratory received 5,762 non-gynecologic specimens with urine excluded. Immunocytochemistry was performed selectively in problematic cases. A total of 215 stainings including 124 epithelial markers, 50 lymphoma/leukemia markers, 22 neuroglial and choroid plexus markers, seven mesenchymal markers, six melanoma markers, and six others was performed on I45 specimens consisting of 89 effusions, 28 fine-needle aspirations, I I cerebrospinal fluids, and I7 other specimens. Eflusions were by f a r the most frequent specimens for immunocytochemistry and the epithelial markers were the most frequently used antibodies. The immunocytochemical results were essential in 41 specimens (28%). confirmatory in 37 (26%), and non-contributory in 67 (46%). Essential and conjirmatory results occurred in 49% of effusions (44/89), 71 % of fine-needle aspirations (20/28), 55% of cerebrospinal jluids (6/I I), and 47% of other specimens (8/17). It is concluded that immunocytochemistry is proved to be a good aid for the final diagnosis of daily cytologic practices in which the fine-needle aspiration specimens are benejitted best.