Sialorrhoea can be a significant problem in both adults and children and can cause both physical and psychosocial problems. Botulinum toxin has enjoyed an emergence in the treatment of sialorrhoea, a systematic review of the evidence for botulinum toxin reveals two randomised controlled trials (RCTs) and four other trials that fulfilled our inclusion criteria. Both RCTs demonstrate the effectiveness of botulinum toxin in the management of sialorrhoea. There was no clear evidence for one antigenic type of botulinum toxin over another and minimal evidence for the optimal dose of botulinum toxin for each antigenic type. No advantage is conferred in using ultrasound guidance in injecting the glands. None of the RCTs or other studies directly compared submandibular versus parotid injection or directly compared botulinum toxin against surgery. Minor side effects were reported in one of the RCTs but overall botulinum toxin is a safe, minimally invasive and effective means in the treatment of sialorrhoea with the potential to become the treatment of choice. Our review demonstrates that further randomised controlled trials are required to more fully evaluate this new modality of treatment.