he resazurin test is conducted similar to the methylene blue reduction test with the judgement of quality based either on the color produced after a stated period of incubation or on the time required to reduce the dye to a given end-point. Numerous modifications have been proposed. The two most commonly used are the "one-hour test" and the "triple-reading test" taken after one, two, and three hours of incubation. Other modifications have value in specific applications.