Background: 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 (HiTOP; Kotov et al., 2017) or the “Big Five” for personality. This paper addresses three major barriers to establishing such a taxonomy: 1) a lack of research explicitly comparing categorical (subtype) versus dimensional models; 2) primary reliance on trait (between-person) measures rather than multilevel models in the extant literature; 3) insufficient emphasis on replication and refinement.Methods: Participants included an unselected crowdsourced sample (691 observations from 248 participants) and an independent anxious-depressed replication sample (757 observations from 260 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. Support vector regression machine learning probed the validity of features and dimension for predicting established trait measures.Results: 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 content, and uncertainty.Conclusions: Findings support a five-factor latent structure of PT. Theoretical, empirical, and clinical implications and future directions are discussed.