OBJECTIVES: Botulinum toxin has emerged as an effective approach for the management of sialorrhea. This study presents a critical literature review and meta-analysis to determine the impact of botulinum toxin on drooling severity in patients with sialorrhea. DATA SOURCES: Ovid MEDLINE and the Cochrane databases. REVIEW METHODS: The above sources were searched to identify studies examining botulinum toxin for the treatment of sialorrhea. Included studies were randomized, placebo-controlled trials. Excluded studies failed to report quantifiable outcome measures of drooling severity at 4 weeks postintervention. RESULTS: Eight studies involving 181 patients (83 placebo; 98 active) were included in the analysis. Botulinum toxin was found to significantly decrease the severity of drooling in patients with sialorrhea (standardized mean difference [SMD], -1.54; 95% confidence interval [CI], -2.05 to -1.04; P = .06; I (2) = 48%) when compared with placebo control using random effects models. The effect was significant in both adult (SMD, -1.29; 95% CI, -1.88 to -0.71) and pediatric (SMD, -1.84; 95% CI, -2.67 to -1.00) populations. Both botulinum toxin A (SMD, -1.53; 95% CI, -2.27 to -0.79) and B (SMD, -1.56; 95% CI, -2.32 to -0.79) produced similar effects. Botulinum toxin doses greater than 50 U (SMD, -3.81; 95% CI, -6.19 to -1.43) produced much stronger effects compared with doses less than or equal to 50 U (SMD, -1.32; 95% CI, -2.28 to -0.36). CONCLUSION: Botulinum toxin is a clinically effective therapy that improves drooling severity in patients with sialorrhea. Future studies will need to further evaluate the technique and examine dosages required to achieve optimal outcomes.