A systematic formulation of the higher genus expansion in topological string
theory is considered. We also develop a simple way of evaluating genus zero
correlation functions. At higher genera we derive some interesting formulas for
the free energy in the A1 and A2 models. We present some evidence that
topological minimal models associated with Lie algebras other than the A-D-E
type do not have a consistent higher genus expansion beyond genus one. We also
present some new results on the CP1 model at higher genera.Comment: 36 pages, phyzzx, UTHEP-27