Spliced girder technology continues to attract attention due to its versatility over traditional prestressed concrete highway bridge construction. Relatively limited data is available in the literature, however, for large-scale tests of post-tensioned I-girders, and few studies have examined the behavior of the cast-in-place (CIP) splice regions of post-tensioned spliced girder bridges. In addition to limited knowledge on CIP splice region behavior, a wide variety of splice region details (e.g., splice region length, mild reinforcement details, cross-sectional geometry, etc.) continue to be used in the field. In response to these issues, the research program described in this dissertation was developed to (i) study the strength and serviceability behavior of the CIP splice regions of spliced I-girders, (ii) identify design and detailing practices that have been successfully implemented in CIP splice regions, and (iii) develop design recommendations based on the structural performance of spliced I-girder test specimens. To accomplish these tasks, an industry survey was first conducted to identify the best practices that have been implemented for the splice regions of existing bridges. Splice region details were then selected to be included in large-scale post-tensioned spliced I-girder test specimens. Two tests were conducted to study splice region behavior and evaluate the performance of the chosen details. The failure mechanisms of both test girders were characterized by a shear-compression failure of the web concrete with primary crushing occurring in the vicinity of the top post-tensioning duct. Most significantly, the girders acted essentially as monolithic members in shear at failure. Web crushing extended across much of the test span and was not localized within the splice regions. To supplement the spliced girder tests, a shear-friction experimental program was also conducted to gain a better understanding of the interface shear behavior between precast and CIP concrete surfaces at splice regions. The findings of the shear-friction study are summarized within this dissertation. Based on the results of the splice region research program, design recommendations were developed, including recommended CIP splice region details.