Chronic migraine is the most frequent and disabling complication of migraine. To date, only two drugs have been specifically analysed for the treatment of chronic migraine, topiramate and onabotulinumtoxin A, and in the evidence-based medicine categories, they have achieved level of evidence I and as such, a grade of recommendation A according to current guidelines. Following the PREEMPT paradigm, pericranial intramuscular onabotulinumtoxin A injections show a good efficacy and safety in chronic migraine patients, both in phase III randomized clinical trials and in a pooled data analyses. Onabotulinumtoxin A injections reduce the number of days of headache and migraine, they reduce the consumption of triptans and disability, and improve the quality of life of migraine patients. For these reasons, onabotulinumtoxin type A is an option as valid as topiramate for the treatment of chronic migraine.