BACKGROUND Allergan Inc. recommends that its botulinum toxin type A (BTX-A; BOTOX) must be refrigerated and applied within 4 hours after its reconstitution to avoid losing its biologic effectiveness. OBJECTIVE The objective was to compare clinical efficacy in treating external canthus dynamic lines with reconstituted and refrigerated toxin (BTX-A) 1 week before its application versus fresh toxin (BTX-A). METHODS This study was a double-blind, randomized, clinical trial. A total of 30 patients aged 30 to 60 years having a minimum of one and maximum of six external canthus dynamic lines were treated in one canthus with 15 U of BTX-A reconstituted and refrigerated at 4°C 1 week before being applied and in the other with 15 U of fresh BTX-A. Patients were followed-up on Day 10 and Weeks 6, 12, and 18; assessment included a neuroconduction study of the facial nerve and the investigators' photographic evaluation of the number of external canthus dynamic lines at maximum smile. RESULTS Outcome measurement did not show statistically significant differences between both groups. CONCLUSION BTX-A, reconstituted and refrigerated 1 week before its application, has similar clinical efficacy in treating external canthus dynamic lines as does fresh BTX-A.