Sixty extracted human teeth were divided into three groups of 20 each. Apically extruded debris and irrigant were collected, dried, and weighed by the following three instrumentation techniques: (a) group 1, filing 1 mm short of the foramen; (b) group 2, Canal Master instrumentation to the foramen; and (c) group 3, filing to the foramen (for a relative comparison). The results indicated that all three groups were significantly different from one another. Group 1 had the least amount of debris extruded. Of the two groups instrumented to the foramen, group 3 had twice as much debris extruded as group 2. An apical dentinal plug was frequently found in group 1 and was probably a major reason why this group had the least amount of extruded debris. The significance of this dentinal plug and possible indications for instrumentation to the foramen are discussed.