During the STAAARTE 96 Hellen aircraft campaign the lidar ALTO together with in situ measurements examined the ozone and aerosols variability in the lower troposphere over the Eastern Mediterranean region. Ozone mean value in the free troposphere (FT) measured from ALTO was 48 ppb, while it was 45 ppb from in situ observations; the aerosols mean scattering coefficient (550 nm) was 31 Mm-1. The FT ozone distributions of the two instruments are significantly different to distinct sampling. Air masses origin examination using the FLEXPART model for low and high FT ozone observations during late summer indicate that low ozone masses come from Mediterranean/North Africa regions travelling at low altitude, while high ozone masses emanate from Europe’s middle or upper troposphere.