BACKGROUND. This is the first reported study of histologically confirmed migration from intravenous access devices in children. METHODS. The capsules from around intravenous access devices were examined by light microscopy to determine the extent of the foreign body response; energy dispersive x ray analysis was performed to document the elemental content of the foreign material. RESULTS. A fibroconnective tissue capsule was found around all the samples. Elemental silicon was found in six of 13 tissue samples, and a foreign body giant cell reaction was seen in three of these. CONCLUSIONS. The pseudocapsule that surrounds an implanted vascular access device often has residual foreign material, including silicone.