BACKGROUND/AIMS: To evaluate the factors which are related to the transition from achalasia to diffuse esophageal spasm (DES) or nutcracker esophagus (NE) after botulinum toxin injection to lower esophageal sphincter (LES). METHODS: This study included the 23 patients with achalasia who received an intrasphincteric injection of botulinum toxin. Stational esophageal manometry, 24-hour ambulatory esophageal manometry with pH monitoring, barium esophagogram and endoscopic ultrasonography were performed before and after treatment. We analyzed the parameters from these studies between the cases that transformed to DES or NE within a week and the cases that do not transit. RESULT: Five patients (21.7%) transformed to DES (1) or NE (4) within a week. There were significant differences in contraction amplitude of esophageal body (median, 31 mmHg vs 23 mmHg, p < 0.05) and maximal diameter of esophageal body (median, 2.6 cm vs 4.4 cm, p < 0.05) between these five patients and the remaining patients. There were no significant differences in sex, LES pressure and thickness of muscle layer between two groups. CONCLUSION: Factors involved in transition to NE or DES after botulinum toxin injection to LES of achalasia appears as high amplitude contractions in body of esophagus and less dilation of esophageal body.