1. An evaluation was made of methods and equipment used for microtitration. 2. The simplicity, accuracy, reproducibility, time saving and economy of microtitersystems well substaniate their use over other outdated methods. 3. Microtiter systems have been found to be useful in agglutination, complement fixation, conglutination and hemagglutination procedures in disease processes caused by bacteria, rickettsia, viruses, fungi, protozoans, metozoans and certain allergic manifestations. 4. A method combining the use of microtitration and an Autoanalyzer has been presented. The microtitraters provided a rapid, accurate and economical method for the preparation of dilutions in plastic cups, which were then fed through either a complement fixation or a hemagglutination manifold for analysis. These were passed through a flow-cell colorimeter and the results, compared with standards, were recorded. This produced an exceedingly sensitive and accurate endpoint. 5. The combined Microtiter-auto-analyzer method provided a simple and precise procedure for continuously titrating hemagglutins and complement fixing antibodies with a reproducibility of ±2.3%.