To evaluate the occluding effect of five desensitizing agents on human dentin tubules.30 buccal and lingual surfaces were prepared from 15 extracted intact third molars. Each surface was polished with aluminum oxide abrasive papers to remove enamel and to expose the underlying dentin in cervical area. The flat dentin surfaces were treated with 0.5 M EDTA for 2 minutes to expose dentin tubule orifices. The samples were randomly divided into six groups: AS - immersed in artificial saliva at 37 degrees C for 2 weeks (control); OX - Oxagel (monopotassium oxalate), DU - Duraphat (sodium fluoride), DE - Desensibilize (strontium chloride), OD - Odahcam (acidulated phosphate fluoride) and SE - Sensodyne (strontium chloride + calcium carbonate abrasive). Dentin desensitizers were applied during 2 weeks and after each application the samples were kept in artificial saliva at 37 degrees C. The samples were prepared according to the scanning electron microscope procedures and were examined at x2000 magnification.The results were expressed in percent (%) of tubule occlusion and analyzed by ANOVA and Duncan's multiple range test (P < 0.05): AS- 45.41 +/- 11.65a; OX- 42.65 +/- 11.79a; DU- 47.25 +/- 8.59ab; DE- 49.36 +/- 18.27ab; OD- 64.43 +/- 15.55b and SE- 65.44 +/- 10.93b. Results suggest that the dentin surfaces treated with OD and SE showed higher tubule occlusion when compared to AS and OX, but were not different compared to DU and DE treatments.