In March 1979, millimeter-wave observations of the ozone emission line at 101737 MHz were made to measure the diurnal variations in mesospheric ozone. Changes in mesospheric ozone were measured diurnally for a 10-day period. The ozone column above ~76 km rapidly decreased after sunrise to half value within 1 hour and was then followed by a slower (~8 hours) decrease to an absolute minimum at 1600 hours. At sunset, the ozone column above ~76 km increase rapidly to its maximum value within 2 hours. In the 48--68 km altitude range, the ozone changes were gradual within gradul with a minumum near local noon (1200 hours).