Vertical distributions of ozone observed at Albuquerque, New Mexico, and at Fort Collins, Colorado, on 5, 6 and 7 May 1963 by means of the chemiluminescent ozone-sonde are compared with the structure of the wind and temperature fields during this period. The comparison indicates that during the passage of an upper trough, accompanied by a trough in the conventionally defined middle tropopause, the increase in partial pressure of ozone with altitude begins at a level considerably lower than the level of the tropopause. In general, secondary maxima in the partial pressure of ozone between the level of the main ozone maximum and the level of the middle tropopause at the time of the sounding are associated with tongues, or layers, of polar or middle-latitude stratospheric air injected into tropical air. Tongues of tropical air injected into higher-latitude stratospheric air are associated with a decrease in the partial pressure of ozone. Small-scale features as well as large-scale features of such interpenetrations of polar or middle-latitude stratospheric air and tropical air, as indicated by the temperature field, are substantiated by the ozone soundings.