The Persian language has up to the present been described principally in its classical form. Persian as it occurs today in an abundant literature is not identical with the classical language. Colloquial language diverges from it appreciably more; it merits all the more attention since not only is it the common language of the day-to-day relations of all classes of society, but also because the recent literary rebirth has caused it to penetrate ever further into the literature. This is why it is only legitimate to attempt a description of the grammatical system of contemporary Persian as it is written and spoken, based on the usage of Tehran. It is hoped that this grammar may be useful to those who teach or who study Persian, as well as to linguists wishing to get detailed information on the language of contemporary Iran.