Objective: the aim of this study was to evaluate the effect of preparation margin design and construction technique, on marginal accuracy of two provisional crowns. Materials and methods: 40 intact mandibular teeth were used for this study. They were divided in to two major groups (20 each) group A (protemp crowns) and group B (Conventional provisional crowns). Each of these teeth were further divided into group I (shoulder finish line) and group II (chanfer finish line) 10 for each group. Each of these group were further subdivided into subgroup "a" (relined) and subgroup "b" (non - relined) 5 for each group. Results: showed a statistically significant difference in marginal adaptation between different groups at P value of ≤ 0.05 . The group of protemp shoulder non- relined showed the lowest marginal discrepancy (9μm), where as the highest marginal discrepancy was for the conventional chamfer nonrelined group (126 μm). Conclusion : protemp as a material produced the best marginal adaptation on shoulder finish line. In addition protemp does not need relining to produce a perfect marginal adaptation.