RESUMEN
In scientific meetings, researchers present their research findings specially those derived from their dissertations. The scientific identity of the universities depend on the quality of these scientific documents. The more the principles of writing are observed in these dissertations, the more easily and fluently the writer's message is transferred to the readers. This is a descriptive study in which the mistakes in MS and MB students' dissertations were classified into five groups: spelling grammar, puncutation, organization and content. The data were anayzed by descriptive statistics. 18.92% of mistakes were typographical. In 13.61% of cases Hazmzeh was not written correctly. The most frequnet mistake was organizational and the least frequent one was grammatical. The findings revealed that in order to improve the quality of dissertations, students should pay more attention to spelling of words, punctuation, how to write Hamzeh, whether to connect the letter [B] to the noun or verb and whether to connect two words or not