At the Institute of Computer Design and Fault Tolerance (University of Karlsruhe) novel methods for efficient in-line defect diagnosis were developed by manufacturing and measuring test chips in-line side by side with product chips on the same wafer with the same probe-card and the same measurement equipment. For that, test chips have to use the same boundary pad frame as product chips and will be measured with a digital tester. In spite of the limited number of pads, novel methodologies allow to partition the whole chip area into a large number of separable and distinguishable subchips. Thus we get a precise localization of systematic and also small random defects. To analyze the measured data, novel algorithms were developed and implemented in a program system. The in-line process control yields information about different types of defects and statistical data on defects.