Introduction: The present study was performed to determine which duration of BLS training course would maximize learners’acquisition in CPR and AED skills. Material & Methods: 485 participants for this study were non-medical college students who applied for BLS training course from 4 universities. Participants were individually randomized to one of four training groups according to the duration of BLS training course (40~180 minutes). Results: There was no significant difference between level 1 and 2 training groups in performing Hands-only CPR skills after each level of BLS training course. However, there was a significant increase in the proportion of adequate chest compression (p-value<0.001) and average chest compression depth (p-value=0.003) between level 3 and 4 training groups. In addition, significantly more participants in the level 2, 3 and 4 training groups achieved overall AED competency compared to level 1 training group (Table 1). Conclusion: The BLS training increases laypersons’willingness to perform bystander CPR and to use an AED on a cardiac arrest regardless of the duration of training course. However, proficient duration of BLS training should be made available for the lay person to achieve high-quality conventional CPR and AED competency.