Since one can recognize the diversity of the graphic and formal variants of Elamite words and names with particular clearness in the renderings of the Old Persian month-names, the present book makes an attempt to study the questions concerning the relations between the Elamite spellings and the Old Iranian original forms for that group of words in a systematic way. They are suitable for such an examination in an absolutely perfect manner owing to the frequency of the attestations and to the great number of the graphic and formal variants, not least, however, owing to the established identity of content, too. Here one has to take into consideration also the references of the Old Persian forms themselves, which together with the forms attested in Elamite shape must be studied in the greatest possible detail as regards phonology and morphology, but also dialectology and etymology. Two particular results are of some interest: On the one hand several of those month-names can be understood only as being derived from the name of some festival; and on the other hand about half of them show reflexes also of non-Persian dialectal forms, so that we have to conclude that these so-called Old Persian month-names were known also to other Iranian tribes apart from the Persians. Extensive indexes make the many formal details discussed here accessible to the reader.