A theory of compositional viscous fingering with no adjustable paramet
ers that reduces to the Todd and Longstaff model for miscible floods i
s presented. The theory gives excellent predictive agreement with simu
lation results for a wide range of recovery processes. The high-resolu
tion compositional simulations used to validate the theory are the fir
st to resolve viscous fingering adequately in flow other than miscible
flow.