AIM: To compare the effectiveness of two basic life support (BLS) training interventions. METHODS: This experimental trial enrolled 1301 lay people in BLS training. The participants were cluster randomised to either self-learning training or to traditional instructor-led training. Both groups used the Mini-Anne Kit (Laerdal Medical, Stavanger, Norway) and standardised film instructions. After training, the participants practical skills were measured on a Resusci Anne manikin and an AED trainer with the PC SkillReporting system (Laerdal Medical, Stavanger, Norway). The primary outcome was the total score from the modified Cardiff Test of basic life support with automated external defibrillation (19-70 points), six months after training. The secondary outcomes were total score directly after training and quality of individual variables, self-assessed knowledge, confidence and willingness to act, directly and six months after training. RESULTS: For primary outcome six months after training there was no statistically significant difference (p = 0.44) between the total score for the self-learning group (n = 670; median 59, IQR 55-62) compared with the instructor-led group (n = 561; median 59, IQR 55-63). The instructor-led training resulted in a statistically significant higher total score (median 61 versus 59, p < 0.0001), self-assessed knowledge and willingness to act, directly after training (secondary outcomes) compared with the self-learning training. CONCLUSIONS: There was no statistically significant difference in practical skills or willingness to act when comparing self-learning training with instructor-led training six months after training in BLS. However, directly after the intervention, practical skills were better when the training was led by an instructor.