Caffeic acid, fukinolic acid as well as cimicifugic acids A, B, E and F isolated from the rhizomes of Cimicifuga racemosa (Ranunculaceae) inhibited the activity of neutrophil elastase (EC 3.4.21.37) in a dose-dependent manner. An IC50 of 93 μmol/L was determined for caffeic acid and 0.23 μmol/L for fukinolic acid. Cimicifugic acid A inhibited the enzyme with an IC50 of 2.2 μmol/L, cimicifugic acid B with 11.4 μmol/L, and cimicifugic acid F with 18 μmol/L. Cimicifugic acid E was only a very weak inhibitor.