On the Fourier--Jacobi coefficients of certain Eisenstein series for a unitary group by Timothy J. Hickey Doctoral Dissertation, University of Chicago, 1986. ABSTRACT (text-based) The purpose of this dissertation is to develop an explicit formula for the Fourier-Jacobi coefficients of certain adelic Eisenstein series on the non-tube domain GU(2,1) by extending a technique used by Siegel, Baily, Tsao, and Karel in the context of rational tube domains. This work also relies on results of Shintani concerning the Fourier-Jacobi coefficients of those modular forms on GU(2,1) which are simultaneous eigenforms of the Hecke operators. Our main theorem provides a formula for the Fourier-Jacobi coefficients of certain Eisenstein series of weight k associated to Hecke characters of the imaginary quadratic field K which is used to provide a Q-structure for GU(2,1). The formula is deduced from an expansion of the Eisenstein series which is closely related to the Fourier-Jacobi expansion and which has the form of an infinite sum of terms indexex by primitive adelic theta function. Each term is a product of (1) an explicit monomial of Hecke and Dirichlet L-series for the specified character and weight, and (2) a theta function obtained by applying formal Dirichlet series of operators to the indexed adelic theta function. The Dirichlet series consists of operators on the graded ring of adelic theta functions and can be expressed in terms of the eigenvalues of the Eisenstein series by a result of Shintani. A consequence of this explicit formula is the arithmeticity (in the sense of Shimura) of the Eisenstein series.