Since the second edition of the International classification of headache disorders (ICDH-II 2004), chronic migraine has been listed amongst migraine complications. Compared to episodic migraine the prevalence of chronic migraine is low, its impact, however, significant. Until recently no prophylactic drug had been approved for chronic migraine prophylaxis. After case reports had stated an effect of botulinum toxin type A on migraine, several randomized placebo-controlled studies were conducted in episodic headache; the results, however, were disappointing. Only when botulinum toxin type A was used in chronic migraine in the PREEMPT (phase 3 research evaluating migraine prophylaxis therapy) trials, its superiority compared to placebo was established. Thus, for the first time a prophylactic drug against chronic migraine is available which is both effective and well tolerated. Botox® has been licensed in England for the prophylaxis of headaches in adults with chronic migraine in 2010. Approval for its use in Germany has been applied for.