This study examined 3 graduate-level online courses that utilized problem-based learning (PBL), considering each course as a case. Beyond describing how PBL was implemented in each case, this study identified what worked (strengths) and did not work (weaknesses) in the PBL and explored how the PBL could be improved (improvements) by collecting both descriptive and evaluative data. Data were collected from interviews, observations, and document review. Based on cross-case analyses, this study proposed a series of guidelines for designing and implementing PBL in online environments. They provide practical tips for diverse stages of the design and implementation of online PBL. (Contains 1 figure.)