  I review recent theoretical treatments of a dilute interacting condensed Bose
gas in a trap. Bogoliubov's classic results for a uniform condensate are
generalized to include the effect of a trap, using the Gross-Pitaevskii
formalism (for the condensate) and the Bogoliubov equations (for the linearized
small-amplitude excitations of the condensate). Several recent theoretical
studies are discussed along with some open questions.
