Aims: To evaluate the effectiveness and safety of botulinum toxin administration into the inferior head of the lateral pterygoid muscle of patients with jaw opening dystonia by using a computer-aided design/computer-assisted manufacture (CAD/CAM)-derived needle guide. Methods: A total of 17 patients with jaw opening dystonia were enrolled. After the patient's computed tomography (CT) scan was imported and fused with a scan of a plaster cast model of the maxilla, the optimal needle insertion site over the lateral pterygoid muscle was determined using the NobelClinician software. A total of 13 patients were injected both with and without the guide, and 4 patients underwent guided injection alone. The therapeutic effects of botulinum toxin injection and its associated complications were statistically compared between the guided and unguided procedures using paired t test. Results: Botulinum toxin therapy was performed 42 and 32 times with and without the guides, respectively. The needle was easily inserted without any complications in all procedures. There was a significant difference (P .001) between the mean comprehensive improvements observed with (66.3%) and without (54.4%) the guides. Conclusion: The findings suggest that the use of needle guides during the injection of botulinum toxin into the inferior head of the lateral pterygoid muscle is very useful for aiding the accurate and safe administration of botulinum toxin therapy for jaw opening dystonia. Keywords: botulinum toxin therapy, computer-aided design/computer-assisted manufacturing, jaw opening dystonia, lateral pterygoid muscle, oromandibular dystonia