The official history of the Later Han dynasty (AD 25-220) contains eight so-called Treatises, traditionally regarded as accurate descriptions of the dynasty's institutions. Practically all literature dealing with the bureaucratic system, the geography, the religious beliefs or the calendar of the first two centuries AD is based on these Treatises, even though their value as source material has never been critically examined. This study subjects each of the Treatises in turn to a detailed scrutiny. The sources used by the Chinese historian and their adaption to suit his historiographical tastes, the opinions of previous critics and the weight of the available evidence all pass review in order to arrive at a balanced view of the historiographical value of each individual Treatise.