Two fundamental insights underlie most recent researches on language development. The first is the realization that the child does not merely speak a garbled version of the adult language around him. Rather, he speaks his own language with its own characteristic patterns. Thus, it is quite appropriate to study a child as the speaker of a specific language to describe its structure by means of a "grammar". The second insight is that the child himself must act as a linguist: he/she is faced with a finite set of utterances from which he must extract the underlying rules in the remainder of his/her life. As far as the universal aspects of language are concerned, many languages must be examined all over the world, and as far as I have investigated, no systematic major study has so far been done on the acquisition of Persian. This point is supported, by the personal report obtained from Julia S. Falk (Michigan State University) who writes: "I know of no major studies on children"s acquisition of this (i.e., Persian) language, and therefore your study could provide an important contribution to knowledge ...". The subject of the study was the language performance of the author"s own child. This study took a long time to collect the required data of her daily productions. The main concern was the subject"s cognitive development to see: 1. At what stages she relates sounds to meaning. 2. Her phonomorphosyntactic and cognitive development. 3. The traces of language universals in the acquisition of Persian language compared with the facts about the universals in other languages. A careful study, that is, the precise observation, taking notes on the subject"s behaviour, and tape-recording, started when she was only seven months old and went on till she became 34 months old. For 27 months, over 700 notes were written on her productions. All sounds and sound combinations which she produced were related to certain meaningful actions: they were also recorded in four cassettes to make further checks possible. They helped me control the written notes in order to provide a more accurate phonetic transcription. Her 27-month productions have been divided up into five different stages. Each stage has clearly pictured the developmental processes of the Persian language; that is, phonomorphosyntactic and cognitive development. Each stage is provided with its related tables. Appendices A and A Cont. present the "Final -Table" introducing the subject"s phonological development from 7 to 34 months of age. Appendix "B" introduces the outline of these stages.