The authors describe the development and validation of the Cognitive Style Indicator (CoSI) using 3 diverse samples (N = 5,924; N = 1,580; and N = 635). Reliability, item, and factor analyses demonstrated the internal consistency and homogeneity of 3 cognitive styles: knowing, planning, and creating. The authors also found substantial support for the instrument's convergent and discriminant validity by including other cognitive style instruments and personality and academic performance measures in the validation process. Criterion-related validity was confirmed by examination of the relation between these cognitive styles and work-related characteristics. The main contributions of this study are (a) the further refinement of the analytic-intuitive cognitive style dimension by splitting the analytic pole in a knowing and a planning style and (b) the development of a valid and reliable cognitive style instrument for use in organizations.