The gel of silicone implants may bleed through the elastomeric envelope or may come into contact with the body because of rupture of the implant. We have studied the effects of free silicone gel injected into the subcutaneous space in rats and analysed the morphological features of the axillary and inguinal lymph nodes. Ninety six Wistar rats had 3 cm3 of silicone gel injected into their subcutaneous space and 96 Wistar rats (the control group) had distilled water injected into their subcutaneous space. The animals were killed on days 1,3,7,9,15, 30,60,90,120,180,270, and 365 after the injection. There was no detectable silicone and no damage to the lymph nodes on routine histopathological analysis. Small amounts of silicone that could migrate to lymph nodes could result in hyperplasia. To evaluate this possibility, a morphometric study based on a computer aided system compared the area of lymph node sections between treated and control animals, and showed no difference between treated and control groups. If silicone did migrate, it did not provoke morphological signs or hyperplasia in the lymph nodes.