The sputa of patients with chronic obstructive lung disease show high histamine concentrations with large individual variations. The fluorometric and the biologic method correlate statistically significantly. Histamine concentrations decrease significantly, during 60 min at 37 degrees C, by different amounts in different patients. The measured histamine concentration can cause bronchoconstriction. The histamine and the NaCl control solutions have been found to liberate histamine into the blood, measured as free plasma histamine. There are still many questions open which should be solved because the histamine concentration in the sputum could play an important role in chronic obstructive lung disease.