To measure markers of leukocyte activation in patients with an exclusively ocular inflammatory or bacterial disease. Neutrophil myeloperoxidase, eosinophil cationic protein, eosinophil neurotoxin, and soluble interleukin-2 receptor were measured in serum and tears of 17 patients with allergic vernal keratoconjunctivitis, seven with atopic keratoconjunctivitis, 11 with seasonal allergic conjunctivitis, seven with giant papillary conjunctivitis, 13 with rosacea blepharokeratoconjunctivitis, seven with bacterial conjunctivitis, and 13 normal subjects as controls. In serum of patients with vernal and atopic keratoconjunctivitis, levels of eosinophil cationic protein, eosinophil neurotoxin, and interleukin-2 receptor were significantly increased compared with control subjects but were not correlated with the severity of ocular symptoms. In tears of patients with vernal and atopic keratoconjunctivitis and seasonal allergic conjunctivitis, as well as in the nonallergic diseases, rosacea blepharokeratoconjunctivitis and bacterial conjunctivitis, levels of eosinophil cationic protein, neurotoxin, and interleukin-2 receptor were significantly increased compared with control subjects. The highest values of these markers were found in vernal keratoconjunctivitis samples. Neutrophil myeloperoxidase was significantly increased in vernal and atopic keratoconjunctivitis, rosacea blepharokeratoconjunctivitis, and bacterial conjunctivitis. In vernal keratoconjunctivitis, tear markers were correlated to the clinical score of the disease, but not with cytology. Tear histamine was measured in 10 allergic patients after allergen challenge. Although none of the above markers can be considered specific to a single disease, their measurement may still be useful for the quantification of local cell activation in ocular inflammatory diseases.