Background and Aim: The primary energy for speech production is prepared by breathing flow. As there was no index for the maximum phonation time(MPT) to compare normal and speech disordered speakers in Iran, the purpose of this study was to establish this standard for guidance school students in Tehran. 
Materials and Methods: This cross-sectional study was performed on 576 guidance students from 1^st, 5^th, 8^th, 10^th, 15^th and 19^th educational regions. Each student made an usual inhalation and produced the /a/ for three times with the maximum strength but in a way that he/she didn&apost feel tension on his/her neck or larynx. The maximum time was recorded as the maximum phonation time.
Results: The results of this research revealed that girls`s MPT in all regions was 15.3, 16.7, and 17.16 seconds and the boys` was 15.41, 16.7 and 17.01 seconds and all students` 15.36, 16.17 and 17.08 seconds in order of their grades. There was significant difference between first and third grade mean MPT (p=0.003).
Conclusion: The result of this study indicates that, as the students age increases their MPT increase, too. Also, boys` MPT was more than girls` in first and second grades however, in third grade the girls` MPT was more.

Background and Aim: The words are the symbolic tools for communication. Nouns are the initial and the most frequent components of language that children acquire and use during the procedure of language development. Therefore, this study aimed to determine the noun perception and expression abilities in Persian-speaking children, as well as gathering the normative data for two picture-pointing and picture-naming tests.
Methods: In this cross-sectional study, 110 normal Persian-speaking children (54 girls and 56 boys), 2.5 to 4 year-old in four groups, were selected randomly throughout Arak kindergartens. Two pictorial perception and expression tests were performed in this study.
Results: Mean scores of perception and expression was statistically different between all age groups, except 3 and 3.5 year-old groups (p<0.05). There was no statistically difference between mean scores of girls and boys. In addition, a significant positive correlation between mean scores of perception and expression was shown (p=0.001, r=0.896).
Conclusion: The perception and expression abilities are different in 4 age groups. The two picture-pointing and picture-naming tests can show these differences. Regardless of rapid development of perception, perception and expression abilities develop in parallel, and the ability of girls and boys shows similar trends.