The list of injectable skin fillers available for soft tissue augmentation is constantly growing, giving aesthetic surgeons more options in the treatment of scars, lines, and wrinkles. Each type of filler is distinct with regard to intended use, placement technique, duration in tissue, ease of use, and cost. Physicians who are well acquainted with the strengths and weaknesses of each class of filler will be best equipped to use this rapidly expanding class of agents in serving their patients. The authors review the most commonly used injectable skin fillers and discuss their differences in terms of composition, source (eg, human, animal), intended use, placement technique, tissue duration (nonpermanent, semipermanent, or permanent), side effects, and specific advantages and disadvantages.