Lidar measurements of the ozone vertical distribution have been performed on a routine basis at the Observatoire de Haute-Provence, starting in October 1986. They provide a unique data base which is used to derive the observed seasonal behaviour of ozone in various altitude ranges from 25 to 45 km with a height resolution much higher than previous operational systems. Comparison with Umkehr measurements performed at the same location show a rather good agreement in layers 5 and 6 with unexpected differences appearing in the uppermost layers. ¿ American Geophysical Union 1989