This thesis addresses two issues related to the problem of reconstructing a one-dimensional or a multidimensional sequence from either the phase or the magnitude of its Fourier transform. The first concerns the development of conditions under which a sequence is uniquely defined in terms of only phase or magnitude information. For example, it is shown that a one-dimensional sequence is, in most cases, uniquely specified by the phase of its Fourier transform if the sequence is finite in length. In the case of magnitude, a condition for uniqueness is presented which is a generalization of the minimum and maximum phase constraints and includes them as a special case. For multidimensional sequences, on the other hand, it is shown that a finite support constraint is sufficient, in most cases, for the sequence to be uniquely defined by either the phase or magnitude of its Fourier transform.The second issue which is addressed concerns the development of algorithms for reconstructing a sequence from either the phase or magnitude of its Fourier transform. In particular, several algorithms are presented for reconstructing a sequence from its phase. These algorithms, which include iterative as well as non-iterative approaches, always lead to the correct solution provided the appropriate uniqueness constraints are fulfilled. An iterative procedure is also described for reconstructing a multidimensional sequence from the magnitude of its Fourier transform. However, the convergence of this algorithm to the desired sequence appears to depend upon the availability of an initial estimate which is sufficiently close to the correct solution. Finally, a number of examples are presented which illustrate the use of these algorithms. -2-