Exposure to tobacco smoke can cause irritation of the conjunctiva. We conducted this study to identify the effect of tobacco on rat conjunctiva. Animals were divided into experimental and control groups and we exposed the experimental group to tobacco smoke. Control group rats inhaled only room air. Spectrophotometric analysis of the smoke-air mixture revealed that many toxic substances were present in this compound. We found very high levels of plasma thiocyanate after exposure to smoke in experimental group animals but no increase in the control group. So, this data indicates that these animals inhaled smoke effectively in our method. After 3 months conjunctivas were examined by light and electron microscopy. In the experimental group, conjunctivas were thinned, atrophied and microvillous projections and desmosomal connections were absent in comparison with the control conjunctivas. This pathologic change is very similar to conjunctival response to chronic irritants of any type.