Gastroesophageal reflux disease (GERD) refractory to conventional medical treatment is frequently associated with gastroparesis, a complex condition with no definitive treatment to date. We first developed a scoring system to assess the severity and frequency of both reflux- and gastroparesis-related symptoms. We then tested, for the first time, the hypothesis that endoscopic pyloric botulinum toxin injection alleviates both of these symptom types. Eleven patients (four males) with GERD (confirmed by esophageal pH monitoring) plus gastroparesis (confirmed by gastric emptying study) underwent toxin injection. Patients had no concomitant disease and were not allowed to use prokinetics before or after treatment. Injection significantly improved both gastroparesis- and reflux-related symptoms in the majority of patients but the duration of symptom relief was relatively short. Responders to treatment had significantly higher total reflux symptom scores (before injection) than nonresponders. All but one of the patients in whom gastroparesis symptoms improved also showed response in reflux symptoms, which supports our hypothesis. We believe that response to toxin injection is a reliable predictor of response to subsequent surgery following the recurrence of symptoms.