A trocar having a working channel extending along an between a distal end and a proximal end includes a cannula at the distal end and a housing at the proximal end which define a working channel of the trocar. A valve disposed in the working channel separates the trocar into regions proximal of the valve and regions distal of the valve. The valve includes elastomeric means which form a first seal that is openably closable across the working channel. A wall of the valve extends radially outwardly of the elastomeric means and forms a second seal with the housing. The trocar also includes means for defining a passage extending from regions exterior of the trocar through the regions proximal of the valve and into the regions distal of the valve. Valve means disposed across this passage controls the administration of fluid through the passage and into the working channel of the cannula.