The objective of this investigation was to determine a limit beyond which further increase in the number of lines of half-tone screens does not improve the quality of multicolor prints. Quality evaluations were based solely on the appearance of otherwise identical prints made with screens of different line widths. Technical difficulties of screening, platemaking, and printing that also depend on screen ruling were disregarded. Different criteria were used: 1) Is the dot structure visible? 2) Is it disturbing? 3) Can details of the image be recognized? The last criterion was considered the most important. Depending on the type of details, the limiting screen ruling was found to be 150 to 200 lines per inch at the distance of ordinary reading. A further improvement by the use of still finer screens was obtained only in very exceptional cases.