['This study examined the change over 20 months in 178 participants with frequent episodic migraine under adequate treatment as usual, who had completed online behavioural training (oBT) in migraine self-management either directly (group 1, n\u2009=\u2009120) or after 10 months of watchful waiting (group 2, n\u2009=\u200958).', 'Participants completed questionnaires and an online headache diary and migraine monitor following the International Classification of Headache Disorders at T0 (baseline), T1 (post-training), T2 (6-month follow-up; extended baseline in group 2), T3 (post-training, group 2 only) and T4 (group 1: 16-month follow-up; group 2: 6-month follow-up). Statistical analyses were conducted on the observed data without imputation of missing observations.', 'Both groups were highly comparable. The data over time revealed benefits in response to oBT, with significant between-group differences in the change achieved in the training episodes T2-T0 (group 1) and T4-T2 (group 2). Improved attack frequency (M\u2009=\u2009-23%) was higher in participants with more (i.e. 4-6) attacks per month at baseline, and the effects of oBT were durable over 16 months of follow-up.'] Does follow-up over 20 months confirm gains of online behavioural training in frequent episodic migraine?