The marginal and internal fit of four different types of ceramic inlays—Cerec, Celay, Empress, and Vita In-Ceram Spinell—was determined after they had been luted on extracted premolars. For the Cerec inlays sharp and U-shaped proximal box shapings were also compared. There was no statistically significant difference either in the proximal fit or in the gingivoproximal fit between the four inlay systems studied, with the exception of the Cerec inlays made for preparations with sharp proximal boxes, which had wider marginal gaps. At the occlusal margins a significant-principle order of the gap width was established. The best internal fit was recorded for the Celay inlays, whereas there was no significant difference in the internal fit between the other systems. For the Cerec inlays the U-shaped proximal box shaping improved the marginal accuracy all around the restoration.