© 2020, Academy of Marketing Science. This study proposes an ideal, four-stage model of construct evolution (emergence → conceptualization → competition → consensus) to explain construct development over time. An in-depth analysis of conceptualizations of two constructs, market orientation (MO) and customer-based brand equity (CBBE), however, reveals different evolutionary stages and trajectories that deviate from the ideal model. The final stage for MO and CBBE is fragmentation, not consensus, characterized by customized operationalizations and variable construct definitions. A supplementary analysis of need for cognition (NFC) and involvement constructs provides additional support. For example, the final stage of NFC is dominance, characterized by nearly complete reliance on standard definitions and operationalizations. Conceptual research, formal measure development, and differing types of constructs all can influence the evolution of constructs. These findings have deep implications for marketing research: Diverse definitions and operationalizations can impede knowledge accumulation. This article proposes guidelines for improving research practices and managing constructs across evolutionary stages.