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Large liquid scintillation counters offer a unique combination of high sensitivity and moderate energy resolution and hence are particularly useful for the rapid measurement of the radioactivity of the human body and other large samples. This counter permits measurements of internal gamma contamination of the human body at concentrations 1000 times less than maximum permissible levels. Such an instrument can, therefore, have many practical applications to diagnosis in clinical and experimental medicine. The instrumentation to be described is used with the new Los Alamos human counter but the techniques are applicable to large liquid scintillation counters in general. Objectives in this system are: 1) optimizing pulse-height (energy) resolution from the detector, 2) optimizing SNR, 3) long-term stability and freedom from rate and overload deficiencies and 4) accuracy, speed and versatility of data handling and processing.