Radial fluid flow in cylindrical and spherical contact metamorphic aureoles produces alteration patterns that are distinctly different from those predicted for cartesian one-dimensional flow. The combined effects of flow focusing and decreasing reactive rock volume during inward flow result in more alteration and steeper alteration versus distance profiles. Applied to contact metamorphism, cartesian models overestimate, by as much as an order-of-magnitude, the time-integrated fluid fluxes necessary to produce observed alteration by inward fluid flow. Outward radial flow is less efficient than cartesian flow because reactive rock volume increases and fluid flux is defocused; cartesian models tend to underestimate the quantity of magmatic fluid required to produce alteration by outward flow. ¿ American Geophysical Union 1995