A B S T R A C TObjective: General practitioners (GPs) disclose more uncertainty (e.g. "I don't know") in consultations with patients presenting medically unexplained symptoms (MUS) versus medically explained symptoms (MES), which could negatively affect patient outcomes. This study assessed if this pattern also holds for more subtle, implicit uncertainty expressions (e.g. "maybe", "might") during different consultation phases, and assessed their relation to patient pre-post consultation anxiety. Methods: We quantified implicit markers of uncertainty of 18 GPs in 82 consultations about MUS or MES during different consultation phases. Relative frequencies of implicit uncertainty per consultation were regressed on differences in momentary anxiety pre and post consultation. Results: We coded 2590 GP utterances. Uncertainty expressions were more frequent in MUS versus MES consultations (OR = 1.54, p = .004), especially during diagnosis and treatment recommendations compared to physical examinations (OR =0 .45, p = .001). Implicit uncertainty was not related to patients' changes in anxiety (b = 0.11, p = .817). Conclusions: GPs express more uncertainty during MUS (versus MES) consultations, especially during the diagnostic phase and treatment recommendations. This does not necessarily affect patient anxiety.Stortbeker, I. , Houwen, J., Dulmen, S. van, olde Hartman, T, Das, E. Quantifying implicit uncertainty in primary care consultations: Asystematic comparison of communication about medically explained versus unexplained symptoms.