Sialorrhea or excessive salivation, and drooling, are common and disabling manifestations in different neurological disorders. A review is made of the literature, based on a PubMed search, selecting those articles describing clinical trials involving the injection of botulinum toxin A in the salivary glands of patients with different diseases characterized by sialorrhea. The most frequently treated diseases were infant cerebral palsy (30%), Parkinson's disease (20%) and amyotrophic lateral sclerosis (15%). Over half of the authors injected the product into the parotid glands, 9.5% into the submaxillary glands, and 38% into both. The total doses of toxin injected varied from 10-100 units of Botox or 30-450 units of Dysport according to the different authors. A reduction was observed in the production of saliva following these injections, and the duration of the therapeutic effect was 1.5-6 months. Six articles (30%) described the presence of adverse effects such as dysphagia, xerostomia and chewing difficulties. Most of the clinical studies involved small patient samples, with no blinding or randomization, and no control group. Moreover, no data are available on the efficacy and adverse effects of treatment in the context of long-term prospective studies. The effective therapeutic dose and ideal form of application remain to be established, and require the conduction of further controlled clinical trials involving large sample sizes.