BACKGROUND Botulinum toxin (BTX) injection is the first choice treatment for focal dystonias. However 10% or more of patients who receive repetitive injections of BTX type A (BTX-A) lose response (secondary non-responders). One of the strategies to manage such patients is to treat them with another serotype. The aim of this article is to describe my experience with BTX type B (BTX-B) in the management of patients with focal dystonia who became secondary non-responders to BTX-A. METHODS Open-label non-controlled use of BTX-B injections to treat dystonia patients who developed secondary nonresponse to BTX-A Response to treatment was rated on a 0-4 scale (Jankovic). RESULTS Four patients entered the study. Pacient 1- At age 48 this man developed idiopathic cervical dystonia. Five years later he also presented with blepharospasm and idiopathic oromandibular dystonia. He was treated with 7604U of BTX-A along 23 sessions separated by a mean interval of 18.8 weeks (range 6-39). Loss of response was noticed after the seventh session. First treatment with BTX-B consisted of injection of 20000U with response rated 3 but duration of 3 weeks. Second session, 23500U, resulted in score 4 with response lasting 12 weeks. Patient 2- This man, with Tourette syndrome since age 8 years, developed tardive blepharospasm at age 51. On 8 sessions of BTX-A injections he received a cumulative dosage of 550U with a mean interval between sessions of 8.8 weeks (range 6-12). Decline of response was noticed after the fifth session. First treatment with BTX-B, 3000U, had a response rated 3 with duration of 12 weeks. Second session, 6000U, resulted in score 4. Patient 3- This woman noticed onset of blepharospasm at age 58 and developed oromandibular and laryngeal dystonia as well as cervical dystonia, respectively, at ages 59 and 65. In other institutions she received 6 sessions of BTX-A. In my service she received a dosage of 1404U along 8 sessions with a mean interval between sessions of 17.4 weeks (range 16-18). She became secondary non-responder after the ninth session. First treatment with BTX-B, 6000U, was rated 0. Second session, 12000U, was rated 4. Patient 4- At age 69 this man developed idiopathic cranial dystonia. Prior to follow up with me, he received 6 sessions of BTX-A in other services. In my institution he was treated with a cumulative dosage of 730U along 4 sessions with a mean interval between sessions of 16.3 weeks (range 15-18). He developed loss of response on the sixth session. Treatment with BTX-B, 12000U, was rated 4 and lasted 20 weeks. Side-effects: local pain (all patients) and dryness of mouth and ptosis (one patient each). CONCLUSIONS My findings confirm that BTX-B injections are a safe and effective option for the management of dystonia patients who become secondary non-responders to BTX-A. The results also underscore the need of individualizing dosage regimens before optimum results are achieved.