Cognitive impairment is a frequent finding in patients with chronic kidney disease (CKD). We examined cognitive performance in a prospective study of 119 patients with CKD stages 3-5 (including dialysis) and 54 control patients of the same age without CKD but with similar vascular risk profiles. Analysis included a comprehensive test battery evaluating memory, information processing speed, executive function, language, and visuoconstructive function, in addition to depression and anxiety. Thirty percent of patients with CKD had cognitive deficits (one or more s.d. below control patient performance). Cognitive deficits (T-value related to published norm values) were mild but significantly decreased to 48.8 in patients with stage 3-5 CKD not requiring hemodialysis and 47.2 in patients with stage 5D disease requiring hemodialysis, compared with 51.5 in control patients. Linear regressions among patients with CKD (forced entry strategy) showed that age (β=-0.50 per s.d.), HbA1c (β=-0.18 per s.d.), and fibrinogen (β=-0.18 per s.d.) predicted cognitive performance. Interestingly, HbA1c discriminated cognition in all age groups, while fibrinogen differentiated cognition particularly in patients over 70 years of age. Thus, our cross-sectional study suggests the severity of cognitive impairment in CKD is mild. As such, longitudinal studies are required to further characterize the role of cognitive deficits in CKD.