[en] Cross sections for the 7P/sub ¹/₂/ → 6D/sub ³/₂/ and 7P/sub ³/₂/ → 6D/sub ³/₂/ transitions, induced at thermal energies by cesium--rare-gas collisions, have been measured over the temperature range from 420 to 615 K. The values of the cross sections are found to be surprisingly high when considering only the energy defect of the levels involved. Moreover, the cross sections for Cs-He collisions exhibit very different behavior than those corresponding to heavier rare gases. A discussion with the aid of theoretical adiabatic potential curves explains the main features of the experimental results. Theoretical calculations of the cross sections have been carried out for some cases, and give results in satisfactory agreement with the experimental values