The transfer of functional muscle tendon units offers the potential for restoration of some facial tone, symmetry and motion after a single-stage procedure in reanimating the paralysed face. Apart from selecting the right donor muscle of adequate strength and excursion, understanding of the correlation between muscle length, tension and force generation is critical. The authors present their data gathered during 13 consecutive temporalis muscle-tendon unit transfer procedures for facial reanimation. Using transcutaneous electrical stimulation of the temporalis muscle, the maximum tendon excursion was measured, while varying the tension applied to the released tendon. The mean excursion of temporalis tendon after detachment from the mandible and electrical stimulation at passive tension was 20.6mm (range, 14-30mm). Based on their findings, the authors discuss indications for when to insert the tendon without an extender, when to extend the temporalis tendon with a graft (e.g. fascia lata), and when to perform a lengthening myoplasty.