It is commonly known that activation of plasma kallikrein-kinin system is of great importance in the pathogenesis of atopic diseases. Plasma kallikrein most likely activates other arginine-esterases in human plasma. Diagnostic and prognostic values of the total arginine-esterase activity and the activity of leukocyte elastase (LE) in plasma of patients with allergic rhinitis (AR), atopic bronchial asthma (ABA) and atopic dermatitis (AD) were examined in this study. Our results demonstrate that the level of arginine-esterase activity was slightly elevated only in plasma of patients with ABA (424 +/- 24; N-360 +/- 20 mU/ml), but not with AR and AD. Elastase-like activity in human plasma proved to be a far more informative indicator of the atopic states than arginine-esterase activity. In plasma of patients with AR, ABA and AD the activity of LE exceeded the normal level in 1.7, 1.8, and 2.4 times, respectively. Treatment of these atopic states with Ditec (Boehringer Ingelheim) led to some improvements of the patient' states. The main component of this drug (disodium chromoglycate) inhibited the activity of leukocyte elastase in experiments in vitro.