Background and Aims: An accurate impression of teeth and supporting structure is necessary to restore a lost tooth structure or to replace a tooth with crown and bridge. Although there are various methods for making impression, putty-wash technique is currently preferred since it is simple and does not require a special tray. Silicone elastomeric impression materials have suitable consistency for putty-wash technique and are thus widely used. Considering the existing controversies over the effects of impression technique on the accuracy of restoration, we evaluated the effects of rewash on the accuracy of stone dies produced by a putty-wash technique. Methods: In this laboratory study, a model with two metallic dies was used. One die had a horizontal notch as an undercut. Ten impressions were made with spacer and ten impressions with rewash technique. A profile meter with accuracy of one micron was used to measure the dimensions of the produced stone models. The original and produced models were compared by t-test. Results: The mean height of dies without undercut decreased significantly in both groups (11.69 with spacer, P < 0.001 and 11.44 with rewash P < 0.001). The mean diameter of dies without undercut decreased in both groups (10.39 with spacer and 10.27 with rewash) but the difference was only significant using rewash technique (P = 0.018). The mean distance between two dies increased in both techniques (30.25 with spacer and 30.43 with rewash). Again, the difference was only significant using rewash technique (P < 0.001). The mean diameter of dies below the undercut increased with spacer technique (10.33; P > 0.05) and decreased with rewash technique (10.21; P < 0.001). The mean height of dies above the undercut decreased significantly in both groups (9.99 with spacer P < 0.001 and 10.21 with rewash P < 0.001). Conclusion: The impression technique with spacer was more accurate in all dimensions as compared to rewash technique.