Biological markers of disease have become increasingly important for the clinician to diagnose, predict and monitor progression, and assess the therapeutic effect of interventions on underlying pathogenic mechanisms. Robust and specific biomarkers would be very useful in inflammation, where they may facilitate early identification of tissue injury, predict disease progression and help to modify disease outcomes. However, at present, there are no robust biomarkers to predict the course of inflammation. Here, we discuss emerging data indicating that RIP2, a putative serine/threonine protein kinase, may serve as a biomarker for the resolution of peritoneal dialysis-associated peritonitis and, more generally, of the acute inflammatory response to infection.