OBJECTIVE: A direct, inverse correlation between 25-hydroxy vitamin D (25(OH) vitamin D) levels and C-reactive protein (CRP), a sensitive biomarker for inflammation, was found in some, but not all, studies. These effects were seen in healthy subjects as well as in some inflammatory diseases. DESIGN AND METHODS: CRP and 25(OH) vitamin D data (2011-2013) from 923 in- and outpatients (males/females 340/583; median age: 76years (95% confidence interval (CI): 75-77) were analyzed. A standardized diagnosis according to the Dutch diagnosis coding standard for each patient was obtained. Each diagnosis was categorized as either inflammatory or non-inflammatory disease. Analysis of variance was performed with age, gender, inflammatory status (inflammatory disease/non-inflammatory disease), and season as corrective factors. RESULTS: The correlation between (log) ln-25(OH) vitamin D and ln-CRP was highly significant (p