The physiology of inflammatory response is modified by the aging process and is substantially affected by multimorbidity and disability. Infection is the most frequent cause of acute inflammation in both adult and older subjects. C-reactive protein (CRP) is the most used biomarker of inflammation, and a substantial amount of literature has demonstrated its importance and clinical usefulness in adult subjects. However, the clinical significance of serum CRP determination has not been completely clarified in older subjects with acute infection, especially in the light of the age-related rearrangements in immunity and cytokine production.