The authors implanted 60 isogenic Balb-C mice, with smooth, fragmented (rough) and poliurethane-coated silicone to evalute the histologic reactions and collagen organization related to these prosthesis. The microscopic observation disclosed the same histologic reaction against the three types of implants. Macrophage-like cells were observed in contact with the prosthesis. The outer portion was constituted, predominantly, by fibroblast-like cells and collagen deposits. The prosthesis geometric shape (or surface) was supposed to orientate the capsule extracelular matrix synthesis. Thus, the authors suggest that the rate decrease of capsule contracture in rough and poliurethane-coated prosthesis is related to a lesser "cell-to-cell"or cell-to-collagen-to-cell" alignment showed by those inflammatory reactions. The use of silicone prosthesis regarding the augmentation of breast volume has been the most widely performed procedure related to this subject. Since its creation by Cronin and Gerow(1), i became evident that the most frequent late complication has been the capsule contracture (2-4). Escape of the silicone gel from the prosthesis lumen, hematoma as well as underclinic infections, has been pointed as etiologic factors(5-15). Thus, some prophylactic measures as the antisepsis of the nipple-areola complex, topic and systemic antibiotic prophylaxis, vitamin E, local massage and external compression, has been advocated by some specialists, but with non-effective results(16,20). Remarkable results were reached in the incidence decrease of the capsule contracture with the use of inflatable prosthesis containing saline solution, associated or not to the steroids, poliurethane-coated prosthesis or rough prosthesis(21,32). Although the literature discloses differences in the inflammatory reactions surrounding the different types of prosthesis surfaces(25), it has not been enphasized that those differences lead to a specific arrangement of the collagen fibers adjacent to the prosthesis and so, altering the capsule contracture rate. This paper was produced to evaluate the histologic reactions and the formation of the collagen capsule adjacent to the different types of prosthesis surface.