This thesis examines existing theories of Spanish stress assignment in generative phonology and proposes an alternative theory that is more effective in predicting the surface representations of Spanish stress. Stress is characterized according to traditional textbook standards and examples are given (Chapter I). The current theoretical setting, especially the theories of James W. Harris, is then described (Chapter II). This writer's own theory, based upon an underlying distinction between tense and lax vowels, is delineated (Chapter III) and defended (Chapter IV). The new stress assignment rule--along with a rule of vowel laxing before a word boundary (#) and a rule of stress adjustment--shows stress in Spanish to be predictable and, therefore, not phonemic.