Critical issues in the theoretical and experimental analysis of interference processes in retention are reviewed. The evolution of classical two-factor theory is traced, and the strengths and weaknesses of the contemporary version of this p6sition are examined. Recent critiques of Current interference theories by Martin (1971a) and Greeno, James, and Da Polito (1971) are reviewed and examind. New conceptualizations of interference proposed by these authors, which place major emphasis on retrieval dependencies and on the role of encoding and retrieval processes, are considered and evaluated.