Introduction: This randomized controlled trial (RCT) investigated the effectiveness of and satisfaction with small-group problem-based learning (PBL) versus a didactic lecture approach to guideline dissemination in asthma management controlling for confounders common in comparative educational interventions. Methods: Sites were selected as either lecture or PBL using simple randomization. All participants were exposed to similar educational resources to ensure treatment equivalency. Instruments included standardized program/speaker evaluation forms and a validated case-based questionnaire with a visual analogue scale measuring the level of confidence of responses. The latter was presented immediately pre- and post-intervention and 3 months later. The statistician was blinded to intervention groups. Results: Overall, 52 family physicians agreed to participate, 23 in the PBL sessions (mean 4.6 per group) and 29 in the didactic lecture sessions (mean 7.25). There was no significant difference between the groups with respect to the knowledge gained at each test administration. Participants rated the lecturer or facilitator equally well as having established a positive learning environment. PBL participants rated the perceived educational value of the program higher than did lecture participants (4.36 vs. 3.93; p =0.04). Both groups experienced a significant increase in asthma-related knowledge post-intervention. Attrition rates for the 3-month post-test were 14% for PBL participants versus 32% for lecture-based participants. Discussion: PBL was as effective in knowledge uptake and retention as lecture-based continuing medical education (CME) programs. Further study is warranted to investigate whether the assessment of higher educational value or an increase in response rate to delayed testing is replicable in other RCTs addressing common confounders and if these factors influence future CME participation, changes in physician clinical behavior, or patient health outcomes.