Respiratory abnormalities in neurocirculatory asthenia (NCAO were analyzed by spirometry and cineroentgenography of diaphragmatic movement. By means of numerical analysis of spirometric curves, irregular intervals of the respiratory cycle, nonuniform amplitude of respiration, nonlinearity of the level of the respiratory curve, and a sighing pattern were observed as characteristic abnormalities in NCA. In addition, an increase in the amplitude of respiration was observed in the acute type of NCA. Analysis of cineroent-genograms revealed (1) irregular periodicity, (2) a nonuniform magnitude of the diaphragmatic movement, (3) superimposition of smaller movements on the larger movements, (4) chaotic and disorganized movement of the diaphragm, and (5) fluctuation in the baseline level of the diaphragmatic movement. Of these abnormalities observed in the movement of the diaphragm, (1) and (2) could be easily predicted by observations of the spirometric curve, and (5) corresponds to the nonlinearity of the spirometric tracing, while (3) and (4) are not recognized in the spirometric curve and indicate that the movement of diaphragm lacks not only rhythmicity but also coordination. These abnormalities may have a role in the development of the cardiovascular, respiratory and gastrointestinal symptoms in NCA. The increase in the amplitude of respiration, observed in the acute type of NCA, resembled findings in the hyperventilation syndrome. Cineroentgenographic analysis of diaphragmatic movement during an attack of tetany in the latter patients, however, showed regular rhythmicity and coordination in contrast to NCA.