We measured tumor-associated trypsin inhibitor (TATI) and C-reactive protein (CRP) in serum of 29 patients with proven pelvic inflammatory disease (PID). TATI values were increased in seven (24%), paralleling increases in CRP. TATI was increased by about 3.5-fold in seven of eight patients with CRP concentrations greater than 90 mg/L, but in none of 21 patients with CRP concentrations less than 90 mg/L. TATI concentration and severity of PID as determined by laparoscopy or endometrial biopsy were not correlated. These results suggest that, in severe infections, regulation of TATI synthesis resembles that of acute-phase proteins.