Purpose: To compare histological and immunohistochemical (IHC) changes induced by prostaglandin analogues, timolol maleate and fixed combinations on rabbit conjunctiva. Methods: 70 New Zealand rabbits were divided in 7 groups of 10 animals. The left eyes were treated with one daily drop of one of the drugs: bimatoprost 0.03%, travoprost 0.004%,latanoprost 0.005%,timolol maleate 0.5%, timolol maleate 0.5%+bimatoprost 0.03% ,timolol maleate 0.5%+travoprost 0.004%and timolol maleate 0.5%+latanoprost 0.005% for 30 days. Following euthanasia and enucleation, the eyes were routinely processed and stained with HE and for IHC using antibodies anti-RAM 11, anti-CD45, CD74, VCAM. Parameters evaluated were: inflamatory reaction, epithelial thickness, number of vessels, vascular diameter and number of goblet cells. One-way ANOVA with a significance level of 5% followed by Tukey-Kramer post hoc tests were used to analyze all numerical variables. Results: All groups of fixed combination presented a significant increase of the inflammatory cell compared to respective isolated prostaglandin: All of them had increase on epithelial thickness and in the number of blood vessels.Ganfort induced an increase in the number of goblet cells compared to Lumigan (p=0.025). The IHQ results showed significant increase of CD45 in all drugs and VCAM increased in G/L (p<0.0001) and XC/X (p=0.04). Duo-travatan compared to Travatan induced increase of expression of RAM 11 (p=0.0002). None of them induced expression of CD74. Comparing FC to timolol, Duotravatan and Ganfort induced increase of inflammatory cells.Xalacom increased epithelial thickness (p=0.0002) and vascular diameter (p=0.04). None of the drugs increased the expression of CD45, CD74 and RAM 11. Conclusions: Comparing fixed combination to isolated prostaglandin analogues, almost all inflammatory parameters increased (epithelial thickness, inflammatory cells and number of blood vessels).