The present study aimed to investigate the vertical marginal gap distance and fracture resistance of two conservative all-ceramic fixed partial denture (FPD) designs in comparison to conventional full coverage-retained fixed partial denture. Three models were created by mounting one cast premolar in an acrylic resin block in conjunction with one of the three cast molars with a 10 mm space between them which corresponded to the dimension of a missing first molar. Fifteen posterior full-contour zirconia-based all-ceramic FPDs were fabricated using CAD/CAM technique and divided into three groups of five samples each according to the type of retainer design:- Group (1): Inlay/inlay-retained FPDs with the inlay retainer on both the premolar and molar teeth. Group (2): Inlay/onlay-retained FPDs with a premolar inlay retainer and a molar onlay retainer. Group (3): Full coverage/full coverage-retained FPDs with full coverage retainers on both the premolar and molar teeth. For all FPDs, the vertical marginal gap distance was measured using scanning electron microscope at 400× magnification. Each mounted chrome-cobalt dies were duplicated into five epoxy resin models for each tested FPD design. The fifteen FPDs were cemented on their respective epoxy resin models with self-adhesive self-cure resin cement. All samples were loaded and fracture loads (N) were measured at fracture with a computer controlled materials testing machine at a crosshead speed of 1.0 mm/min. Fractographic analysis of a representative randomly selected FPD from each tested group was performed using scanning electron microscopy at fixed magnifications (50× and 500×). Within the limitations of this study, the following could be concluded: 1. The marginal gap distance and fracture resistance of three-unit posterior full-contour zirconia-based FPDs are affected by the type of retainers. 2. The inlay/inlay and inlay/onlay-retained FPDs showed higher marginal gap distance than the full coverage/full coverage-retained FPD. 3. The full coverage/full coverage-retained FPD demonstrated the highest fracture resistance. 4. Considering the clinically acceptable marginal gap distance and the maximum chewing forces in the molar region, it seems clinically possible to use full-contour zirconia-based inlay/inlay and inlay/onlay-retained FPDs as conservative alternatives to the full coverage/full coverage- retained FPD.