Measurements of electron temperature and density in the J.I.P.P. T-II device ware made using the Thomson method of scattering ruby laser light. Of all the laser scattering systems ued in tokamak apparatus, the Thomon scattering system when applied to the J.I.P.P. T-II device has the brightest light collecting system ever obtained. The electron temperature could be measured without the viewing dump and light baffles by the use of the high quality filters. The scattered lights are processed by an on-line date-processing computer and the results are displayed graphically in terminals between each shot.