A ruby laser radar has been constructed at Fukuoka (33° N), south-west Japan, for the purpose of probing the upper atmosphere. Observations of stratospheric aerosol layers have been carried out since October 1972. Data obtained show that the layers of enhanced optical backscattering due to aerosols in the height range of 16–30 km were found throughout the period of observation. One of the layers always appeared at about 20 km height and varied to some extent in its height, structure, and peak value of scattering, day-to-day and month-to-month. Other layers appeared in the region above 25 km and seemed more variable. Height profiles of non-Rayleigh backscattering cross section βm are calculated for each night and each month of the observation and compared with the temperature, wind velocity, and ozone concentration in the stratosphere. The individual scattering profile is most likely controlled by the large scale structure of the temperature profile of the night. The mean value of βm in the region around 20 km has its minimum in January and increases from winter to summer. Comparison is also made with the geometrical cross section of the aerosols deduced from the small ion density data and the results show that a large fraction of the aerosol mass is in the range of Aitken particles.