Abstract: A trocar assembly for use in minimally invasive surgery including a housing having an opening formed therethrough and adapted to receive a selected surgical instrument therein. Positioned within the housing is a split seal having a slit extending therethrough. The split seal maintains a seal through the opening of the housing when a surgical instrument is not inserted through the bore of the sleeve. Also positioned within the housing is a seal assembly having a plurality of sealing structures effective to maintain a seal between the housing and a surgical instrument inserted through the bore of the sleeve, such that the plurality of seals accommodate and seal against surgical instruments having different diameters.