Although melting is inferred to start at depths of 120 km or more in the mantle, little is known about the style of melt transport from the source region to the surface. Geochemical observations require the transport of melt from depth to be fast, and that melt is not in chemical equilibrium with the matrix through which it passes. We present a model which allows fast transport by an open melt conduit in a viscous permeable matrix and discuss the possibility of chemical isolation in such a conduit. We show that disturbances on the conduit surface propagate slowly upwards as solitary waves and cause melt to flow between the conduit and the surrounding porous matrix. ¿ American Geophysical Union 1996