Measurements were made to determine the effect of the Reflection Plotter on the visibility of simulated radar signals on PPI screens. Three sizes of target were viewed at 12 inches on a CRT with a P-7 phosphor. These were: small (1 microsec X 1 deg), medium (3 microsec X 10 deg) and large (10 microsec X 30 deg). The data were obtained by the method of attenuating an eight volt signal until a just visible signal was discerned. This measure was expressed in decibels attenuation and was found at screen luminances corresponding to 2, 5.5, 8 and 10 volts of CRT bias beyond visual cut-off for the tube. No noise was used in the tests. Four conditions of visibility were investigated: (1) No Reflection Plotter. (2) Clean Reflection Plotter without edge lighting. (3) Clean Reflection Plotter with faint edge lighting. (4) Dirty Reflection Plotter with bright edge lighting. The results show that the clean Reflection Plotter (condition 2) produced about three db of loss in signal visibility over the condition where no Plotter was used. A brightly lighted Plotter whose surface has been used and wiped to smear the residue of old grease pencil marks (condition 4) produced a seven db loss over the condition where no Plotter was used.