This paper also appears as a chapter in T. Husen and T.N. Postlewaite (eds.) International Encyclopedia of Education: Research and Studies (2nd edition) Oxford: Pergamon Press. It discusses: 1) the historical roots of the term "cognitive style" and various overlapping characterizations of the term; 2) the distinctions between intellective abilities, cognitive strategies and cognitive style; 3) different cognitive styles (e.g. field dependent vs. field independent, cognitive complexity vs. simplicity, reflective vs. impulsive, focussed vs. unfocussed scanning or sharp-focus vs. broad focus scanning, broad vs. narrow categorizing, preference for thematic-relational conceptualizing vs. analytic-descriptive conceptualizing, leveling vs. sharpening or convergent vs. divergent thinking) and how they affect information processing; 4) different learning styles and their orientations toward instruction, specifically meaning, reproducing and achieving orientation; and 5) the question of matching or deliberately mismatching the learner's cognitive style with the mode of instruction to produce optimal learning or flexibility of thought processes.