The design of online or distributed problem-based learning (dPBL) is a nascent, complex design problem. Instructional designers are challenged to effectively unite the constructivist principles of problem-based learning (PBL) with appropriate media in order to create quality dPBL environments. While computer-mediated communication (CMC) tools and the online learning environment provide a natural fit for the PBL process, the tools themselves vary in their affordance to facilitate the design of dPBL. Therefore, the media selection process is more complex, especially for the novice instructional designer who may not have the experience or professional knowledge to select appropriate media for the dPBL learning environment. The purpose of this study was to explore the media selection practices of experienced dPBL instructional designers. Novice instructional designers could benefit from research-based dPBL media selection guidelines drawn from the current practice of experienced dPBL designers. A descriptive case study design was utilized for this study. The researcher conducted in depth, semi-structured telephone interviews with 12 experienced dPBL instructional designers from six different countries. Interview transcripts, artifacts, interview notes, and the researcher journal were used in the data analysis phase. Findings related to the types of media experienced instructional designers utilized to facilitate the design of dPBL included (a) learning management systems, (b) web-based media, and (c) emerging technologies. Findings related to the factors that influenced experienced instructional designers media selection choices included (a) the PBL instructional method, (b) designers' perceived advantages and limitations of asynchronous and synchronous media, and (c) feedback from media pilots. Finally, a list of five interrelated media selection guidelines recommended by the experienced instructional designers included (a) focus on PBL learning activities, (b) integrate synchronous media, (c) explore web-based media and emerging technologies (d) engage in continued professional development, and (e) conduct media pilots. Recommendations for future research included (a) validating the media selection models described in this study, (b) validating the participants recommended media selection guidelines, (c) exploring how and to what extent emerging technologies are being integrated into dPBL design, and (d) comparing the media decision-making processes of experienced and novice dPBL instructional designers. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]