Recent numerical calculations [1,2,3] have shown that Jupiter-family comets, which are on low inclination orbits, cannot originate from the gravitational scatter of long-period comets. Work by Quinn, Tremaine & Duncan [1] shows that objects originally on low-inclination, Neptune crossing orbits will evolve into a population of objects with orbital parameters consistent with those of Jupiter-family comets. However, they point out that the timescale to deplete this initial population of planet-crossing objects is short. Therefore, they conclude there must be a system of objects that are evolving into planet-crossers on the timescale of the age of the solar system. The most likely source of these objects is a region just beyond the orbit of Neptune, the Kuiper belt.