Malnutrition may develop in acute pancreatitis (AP), accompanied by hypermetabolism and high nutritional requirements, and in chronic pancreatitis (CP). We measured the incidence of protein malnutrition in AP and CP by comparing different serum biomarkers of protein metabolism and inflammation. Thirty-five patients with acute (27 moderate, 8 severe), and 35 with chronic, pancreatitis were enrolled in the study. Serum transthyretin, albumin, transferrin and C-reactive protein (CRP) concentrations were measured in AP at admission, after 1 and 2 weeks of jejunal feeding, and in patients with CP at follow-up. In AP, at admission the transthyretin level was low in 74%, transferrin in 48%, and albumin in 29% of patients. In severe pancreatitis, transthyretin levels were significantly lower than in moderate forms (7.5±2.43 vs. 14.39±6.8 mg/dl, p<0.005). Transthyretin levels increased significantly after 2 weeks of jejunal feeding (p<0.05). In CP, transthyretin levels were decreased in 37%, transferrin in 27%, and albumin in 12% of patients. We found significantly lower transthyretin levels in alcohol-related CP than in other forms (18.5±8.3 vs. 30.2±5.7, p<0.01). Transthyretin correlated positively with albumin and transferrin and negatively with CRP. Transthyretin seems to be a sensitive biomarker of protein status and metabolic stress. Monitoring nutritional status through measurement of serum proteins is important for optimal treatment of AP and CP.