Described herein are injection devices capable of automatically injectingsubstances into the soft tissue of a patient.The devices can inject low to high viscosity materials at predetermined, userselected injection rates, allowing the operator morecontrol than a traditional syringe. The devices can allow mixing of more thanone substance and/or reconstitution of a solidsub-stance for injection. The injection devices described herein can allow theoperator to easily inject one or more low to highviscosi-ty liquid or gel soft-tissue augmentation fillers, one or more drugs,one or more other biocompatible materials, or combinationsthereof.
