Statement of problem: Mouth-rinses may soften composite restorations even when the composite is light cured or heat treated. The use of certain mouth-rinses may have less adverse effect on composite restorations.Purpose: The aim of this study was to evaluate the effect of alcoholic and non alcoholic mouth washes on the surface hardness of two types of direct (Z100) and indirect (Gradia) composites.Materials and method: Sixty disc shape samples of Gradia (n=30) and Z100 (n=30) composite were prepared and cured for 40 seconds by halogen light cure unit. Gradia composite specimens were post cured with labolight machine for 5 minutes and then were stored in distilled water for one week at 37c°. The samples were exposed to 3 different solutions of alcoholic, non-alcoholic mouth-rinses, and water for 24 hours at room tempreture. Surface hardness (VHN) was measured and data were analyzed by using One-way ANOVA and Scheffe tests (<0.05).Results: Statistical analysis revealed that, indirect composites which were kept in alcoholic, and non alcoholic solution showed less hardness than control group (water) (p=0.0001). Direct composite specimens which were kept in alcoholic mouthwash had less hardness than control group (p=0.003). Surface hardness of indirect composite specimens kept in alcoholic and nonalcoholic mouth-rinses was significantly higher than direct composites in these solutions (p=0.002 and p=0.008, respectively).Conclusion: Alcoholic and non alcoholic mouth-rinses caused reduction of surface hardness of direct and indirect composites and it seems that the effect of mouth-rinse on surface hardness of these composites is material dependent. Indirect composite showed to be harder than direct composite in all solutions.Key words: Mouth-rinses, Composites, Surface hardness