Introduction: Demonstrating the effectiveness of the rapidly expanding field of electronic continuing education (e-CE) has important implications for CE in the health professions. This study provides an update on evidence from randomized controlled trials (RCTs) assessing the effectiveness of e-CE in the health professions. Methods: A literature search of RCTs was performed in MEDLINE, EMBASE, and CINAHL from 2004 to 2007. Papers were reviewed separately by 2 of the authors and results were categorized and reviewed according to study comparisons. Results: Fifteen studies met our inclusion criteria. Six compared e-CE to no intervention or placebo. Of these 6 studies, 4 showed a statistically significant advantage of the e-CE intervention and 2 showed no significant effect. Two studies compared e-CE to a lecture. Of these, 1 showed an advantage of e-CE and 1 showed no difference. Two studies compared e-CE to a small-group interactive intervention. In both studies, the e-CE group outperformed the control. Two studies compared a multicomponent e-CE intervention to one based on flat text, and both showed the multicomponent intervention to be more effective. Two of the 15 studies demonstrated a statistically significant effect on practice patterns. Positive effects of e-CE on knowledge were shown to persist for up to 12 months and effects on practice up to 5 months. Discussion: Overall, these studies suggest that multicomponent e-CE interventions can be effective in changing health professionals' practice patterns, and improve their knowledge. E-CE interventions based purely on flat text appear to be of limited effectiveness in changing either knowledge or practice. These results support the use of multicomponent e-CE as a method of CE delivery. (Contains 2 tables and 1 footnote.)