OBJECTIVE To evaluate long-term efficacy of intrasphincteric injection of botulinum toxin in untreated achalasia patients; to analyse whether age can be a predictor of response; and to verify whether any objective measurements correlate with symptom relief METHODS A total of 37 patients (mean age 61.4+/-17.5 years) were enrolled, all of whom injected endoscopically with 100 U of botulinum toxin. Symptom score, oesophageal manometry and oesophageal radionuclide emptying were assessed prior to treatment and 4 weeks, 3 months and 1 year after botulinum toxin. In the case of failure or relapse (symptom score >2), treatment was repeated. RESULTS All but 6 patients (83.7%) were in clinical remission one month after botulinum toxin. At 12 months, mean symptom score was 0.9+/-0.5 (p<0.05 vs basal); mean lower oesophageal sphincter pressure was 22.0+/-6.3 (p<0.05 vs basal), and 10-min radionuclide retention was 14.0%+/-7.2 (p<0.05 vs basal). Of the 35 patients followed, 12 (34.3%) had a relapse and were re-treated; 4 out of 12 did not respond after re-treatment. Efficacy of first injection of botulinum toxin lasted for a mean period of 15.6 months (range 2-30). Up to day 31 (83.7%) patients were still in remission. We observed a trend towards a better response to botulinum toxin treatment in patients over 50 years (p=0.053). Moreover no correlation was found between any objective achalasia measurements and symptom relief (r coefficient between 0.1 and 0.5) CONCLUSIONS Results show that: 1) one or two intrasphincteric injections of botulinum toxin result in clinical and objective improvement in about 84% of achalasia patients and are not associated with serious side-effects; 2) patients over 50 years showed better benefit than younger patients; 3) no correlation was found between any objective measurements and symptom relief.