A multi-seal trocar system includes a plurality of co-axial sealing elements adapted for forming a seal with either a large or small instrument. Small and large sealing elements are disposed in an in-line arrangement such that a-single port is provided for instrument insertion. A zero seal is disposed distally of the sealing elements to seal a working channel of the system and to prevent backflow when no instruments are inserted. The small sealing element is configured such that insertion of a large instrument automatically moves the small sealing element out of its path, thereby avoiding contact with the large instrument.