Void-free impression taking is important for the fabrication of accurate dental restorations. One of the essential properties of an impression material used for indirect fabrication of precision castings is the reproduction of the fine detail. The objective in this study was to determine the influence of mixing methods on the number of voids and surface detail reproduction. The number of voids and surface detail reproduction were evaluated with the steteomicroscope $SZ-PT^{(R)}$ and photographed. The results were as follows ; 1. In comparison of the void formation according to mixing methods of all impression materials, mechanical mixing was better than hand mixing and there was significant difference(p<0.05) 2. In comparison of the void formation according to hand mixing of alginate impression materials($TOKUSO;A-1{alpha}^{(R)},;CAVEX;IMPRESSIONAL^{(R)},;AROMA ;FINE;DF;III^{(R)}$), there was no significant difference among alginate groups. But the number of void was increased in the order of $Panasil^{(R)};contact,;TOKUSO;A-1{alpha}^{(R)},;Permlastic^{(R)}$ light bodied and there was significant difference (p<0.05). 3. In comparison of the void formation according to mechanical mixing of alginate impression materials($TOKUSO;A-1{alpha}^{(R)},;CAVEX;IMPRESSIONAL^{(R)},;AROMA FINE;DF;III^{(R)}$), there was no significant different among alginate groups. But the number of void was decreased in order of $TOKUSO;A-1{alpha}^{(R)},;Permlastic^{(R)}light;bodied,;Panasil^{(R)}$ contact and there was significant difference (p<0.05). 4. In comparison of the surface detail reproduction according to mixing methods of 3 types of impression materials($TOKUSO;A-1{alpha}^{(R)},;Permlastic^{(R)};light;bodied,;Panasil^{(R)};contact$), there was no significant difference between hand mixing and mechanical mixing method 5. The surface detail reproduction was only influenced by impression materials, and produced better in order of $TOKUSO;A-1{alpha}^{(R)},;Panasil^{(R)};contact,;Permlastic^{(R)}$ light bodied. There was significat difference among 3 type of impression materials(p<0.05). From the above results, void formation is influenced by mixing methods and surface detail reproduction is influenced by impression materials than mixing methods. Therefore, to fabricate accurate restorations, proper impression material and mechanical mixing method are more effective and available clinically.