Passing time and sometimes imprecise transcription or understanding of ancient texts may cause some mistakes in ancient medical books. This may even lead to some problems in the name or identity of the author or his/her works. In the current study, by careful evaluation of "Al-Hawi" by Rhazes, we extracted the name of 110 physicians and 286 books. The study showed that out of the names, the name of 28 physicians and 20 books were not cited in any medical book or there were mistakes in their identity. For instance, in "Al-Hawi", Rhazes quote from Majhul (unknown) person or book in 208 cases. The study demonstrated that Majhul was an Iranian physician who lived in the 6th century A.D. and was related to the Sassanid Jondishapur University or he was another Iranian scientist, Bedighures, who lived in the first half of the 7th century A.D. We gathered the quotations of Rhazes from the book in the 24 volumes of Al-Hawi and the 40 paragraphs obtained were carefully assessed. According to the results, it seems that the author of the book “Teb-e Ghadim” was Iranian who with high probability lived in early 9th century and had many innovations.