It is known that the pre-junctional functions of the sympathetic nervous system are reciprocal and mutally inhibitory with those of the parasympathetic system just as the two branches of the autonomic system are generally antagonistic at the post-junctional receptor sites. In addition, these regulatory reciprocal mechanisms act to modulate the adenylate/guanylate cyclase-phosphodiesterase system which, in turn, modulates the release of the chemical mediators of the antigen-antibody reaction. Since experimental data from several laboratories suggest that a dysfunction of the sympathetic nervous system exists in bronchial asthma, it is probable that this delicate and crucial balancing has been disrupted. On the basis of these hypotheses, we are studying in healthy anaphylactic, and antigen-sensitized lungs the following: a) the uptake, metabolism and release of catecholamines. b) the inter-relationship between the release of sympathetic and parasympathetic nervous system transmitters. c) the influence of activation of the sympathetic and parasympathetic nervous system on the release of prostaglandins and, in turn, the effects of prostaglandins on the functioning of the sympathetic and parasympathetic nervous systems. d) the changes induced in receptor sensitivity by either repeated stimulation with autonomic nervous system transmitters, antigen sensitization or exposure to the mediators of the anaphylactic reaction. e) the metabolic and ionic conditions necessary for both prostaglandin and histamine release, changes in the cyclic nucleotide levels induced by anaphylaxis, and interactions between the cyclic nucleotides and the release of mediators.