The objective of this study was by morphological and immunohistochemical means to investigate the cellular tissue response to the alloplastic materials polytetrafluoroethylene (PTFE polymer), and soft and hard silicone rubber over time. In seven healthy volunteers implants made of Proplast-Teflon, and soft and hard silicone were inserted subcutaneously in unloaded areas in the iliac crest region. After 1, 2, 4, 12, and 26 weeks, respectively, the implants with surrounding soft tissue were removed en bloc for histological and immunohistochemical examination using a panel of antibodies to various leukocyte markers. The tissue reaction to the various alloplastic materials varied greatly with the focus on macrophage and giant cell reactions and eventual formation of a peri-implant fibrous capsule. The most extensive changes developed next to porous Proplast, both with respect to degree of changes and endurance of tissue reaction. Less intense reactions were seen, in decreasing order, to soft silicone, Teflon, and hard silicone. The study gave no clues to a toxic, allergic, or traditional immunological pathogenesis of the tissue reaction induced by the test materials.