Objective: This study was conducted to evaluate the cosmetic use of bo
tulinum toxin type A (Botox(TM)), which blocks the release of acetylch
oline at the presynaptic neuromuscular junction leading to an irrevers
ible, but temporary chemical denervation muscular paralysis and weakne
ss. This produces a significant cosmetic improvement of wrinkling in t
he upper face due to hyperfunctional animation. Method: A prospective
clinical study representing our experience with this new technique is
presented. Patient selection and evaluation, classification of animati
on lines, techniques, results and complications are discussed. In a 15
-month period, 23 patients with seven anatomic sites were injected. Tw
enty-three patients had the lateral aspect and the inferior aspect of
their squint lines injected, and 26 patients had their glabellar frown
lines injected. Results: Significant improvement occurred to the avera
ge depth and length of the glabellar frownlines. The subjective improv
ement by the patients was also significant. Regarding the crow's feet,
the lateral canthal lines showed more improvement than the inferior l
ateral canthal lines because the latter has a greater component of zyg
omaticus major and minor muscle, which contributes to the inferior lat
eral squint line. Conclusion: Botox is a safe, easy-to-use, effective
modality for the temporary elimination of hyperfunctioning upper-facia
l muscles.