Purpose: The purpose of this study was to investigate the marginalaccuracy of three units fixed partial denture of milled titanium with twomargin designs and two different framework extensions. Materials andmethods: A total of twenty fixed partial dentures replacing missingMaxillary second premolar were constructed on two specially designedand machine craft, stainless steel master models. According to the typeof the finish line the fixed partial dentures were divided into two maingroup each of 10 samples Group I: shoulder finish line. Group II: deepchamfer finish line. Each group was further subdivided into twosubgroups according to the degree of extension of the margin of theanterior retainer as follows: - Subgroup a: framework extended to theouter surface of the finish line. - Subgroup b: framework extended to theaxial tooth preparation 1mm above the finish line. Titanium FPDsframeworks were constructed using CAD/CAM technique as following(Scanning-Designing-Milling) and veneered with low fusing ceramic formarginal accuracy measurment. Vinyl-polysiloxane replica of die /retainers space was made. The replica was sectioned perpendicular to itssurface with a scalpel into four parts (a boucco-lingual section , a mesiodistalsection).Light body vinyl-polysiloxane film thickness wasmeasured under a steremicroscope at magnification (X40). Results :regarless to framework extesion and region of measurement totally it wasfound that shoulder finish line group recorded higher externalgap(57,5.5± 5.5μm) than chamfer finish line group(52,3.1± 6.9μm).Framework extension to the end of finish line recorded higher externalgap (57,5.7±7.5 μm) than positioning 1mm short than finish line (52,2.9±5.5μm). The difference between both finish lines was statisticallysignificant. Conclusion: Both margins tested produced marginal gapswithin the range of clinical acceptance.