['Fabrication of a proper surgical guide is critical for success of implant restorations. The effects of the dimensional factors of the surgical guide on implant placement have not been studied.', 'The purpose of this study was to determine the effect of varied dimensions (diameter, length, and distance between the underside of the surgical guide and the implant recipient site) of a surgical guide on the accuracy of implant angulation.', "In this in vitro study, 240 implant recipient sites were randomly prepared using varied dimensions of a surgical guide. The varied dimensions of the surgical guide's channel and distance were: channel diameter (2, 3, 4, or 5 mm), channel length (6 or 9 mm), and distance between the underside of the surgical guide and the simulated implant recipient site (2 or 4 mm). From these varying dimensions and distances, 16 combinations of dimensions and distances were tested. For each combination, 15 simulated implant recipient site (SIRS) specimens were prepared. The deviated angulation (DA) from the midpoint of the top surface of the 1- x 1-inch simulated implant recipient site (each simulated implant recipient acrylic block contained 5 SIRS of 1 x 1 inch), in the right-to-left (DA(RL)) and front-to-back (DA(FB)) directions, were measured in degrees using a protractor. The data was analyzed using factorial analysis of variance and Tukey's HSD test (alpha=.05).", 'The DA(RL) , in degrees, at a channel length of 9.0 mm (2.33 +/- 1.27) was significantly smaller than at a channel length of 6.0 mm (3.0 +/- 1.42, P =.0001). The DA(RL) , in degrees, at a distance of 4.0 mm (2.13 +/- 1.16) was significantly smaller than at a distance of 2.0 mm (3.16 +/- 1.39, P =.0001). Also, a significant interaction for DA(RL) was found between diameter and distance ( P <.05). For DA(FB) , the varying diameters ( P <.05), lengths ( P =.0001), and distances ( P =.0001) showed significant differences. The DA(FB) at a channel length of 9.0 mm (2.56 degrees +/- 1.51) was significantly smaller than that at 6.0 mm (3.82 degrees +/- 1.87). Significant interactions found for DA(FB) were: diameter by length ( P =.0001), diameter by distance (F=4.547, P =.004), and length by distance (F=11.512, P =.001).'] Do effects of varied dimensions of surgical guides on implant angulations?