Like diagnostic status, clinically relevant thought remains overwhelmingly conceptualized in terms of discrete categories (e.g., worry, rumination, obsessions). However, definitions can vary widely. The area of perseverative thought (or clinically relevant thought more broadly) would benefit substantially from a consensus-based, empirically grounded taxonomy similar to the Hierarchical Taxonomy of Psychopathology (Kotov et al., 2017) or the Big Five for personality. This article addresses three major barriers to establishing such a taxonomy: (a) a lack of research explicitly comparing categorical (subtype) versus dimensional models, (b) primary reliance on between-person measures rather than modeling at the level of the thought (within person), and (c) insufficient emphasis on replication and refinement. Participants included an unselected crowdsourced sample (790 observations from 286 participants) and an independent anxious-depressed replication sample (808 observations from 277 participants). Participants made dimensional ratings for three idiographic clinically relevant thoughts on a range of features. Multilevel latent class analysis and multilevel exploratory factor analysis were applied to identify and extract natural patterns of covariation among features at the level of the thought, controlling for person-level tendencies. A consistent five-dimension solution emerged across both samples and reliably outperformed the best-fitting categorical solution in terms of fit, replicability, and explanatory power. Identified dimensions were dyscontrol, self-focus, valence, interpersonal, and uncertainty. Findings support a five-factor latent structure of perseverative thought. Theoretical, empirical, and clinical implications and future directions are discussed. (PsycInfo Database Record (c) 2022 APA, all rights reserved).