The reasoning that led to the development of hollow-cylinder and hollow-screw implants with an open implant geometry is explained. Important criteria that were investigated in the development phase included: physiologically advantageous load transmission, a biocompatible implant material, and a surface structure favorable to biological stabilization. The reasons the ITI chose an open transmucosal system for its two-part implants are discussed. The rotation symmetrical ITI implants are presented as an integrated system; this features standardized instrumentation and common interchangeable secondary parts. Keywords: implant design, ITI implants, hollow-cylinder implants, hollow-screw implants, osseointegration