The term reduced-diameter implants refers to all implants with a diameter of 3.5 mm or less. However, this blanket classification doesn't do justice to the wide scope of applications and indications these reduceddiameter implants are capable of. Therefore, classification in the following categories has proven useful: Group I = one-piece implant with a diameter less than 3.0 mm (mini-implants). Group II = two-piece implants with a diameter of between 2.9 mm and 3.25 mm. Group III = two-piece implants with a diameter of between 3.3 mm to 3.5 mm. These three groups are currently the focus of scientific efforts and present a potential clinical alternative to complex vertical augmentations. There have been numerous studies published documenting the high success rate of implant survival and patient satisfaction. Systematic reviews confirm these advantageous findings. This makes reduced-diameter implants a promising option for expanding the range of available treatment for narrow interstitial areas in the premolar and anterior regions. The implants are also useful for avoiding complex augmentations on otherwise medically compromised patients.