Twenty-four rectangular metal plates were fabricated with surface regions in three different pore size ranges (5–20 μm, 20–50 μm, 50–200 μm). The plates were implanted into the dorsal subcutaneous tissue of 12 adult mongrel dogs for periods of 4, 8, 12, and 16 weeks. After animal sacrifice, the fibrous tissue which adhered to the porous-surfaced regions of each plate was mechanically peeled off to give an indication of the strength of tissue attachment. The tissue was examined by both transmitted light and scanning electron microscopy. At each time period, the tissue that contacted the porous regions was found to be collagenized fibroconnective tissue. The mechanical tests indicated an increasing strength of tissue attachment with increasing implantation time and pore size range. The largest pore size range of approximately 50–200 μm produced a mean peel strength of attachment of 27.5 g/mm at the 16-week period.