Background and Aim: prosody is a very important factor in communication and includes such parameters as: duration, intonation, pitch, stress, rhythm etc. Intonation is the pitch variation in one sentence. Duration is the time taken to utter a voice. The aim of the present study was to evaluate some parameters of prosody such as duration and intonation curve in interrogative sentences among normal Farsi speaking adults in order to determine the characteristics of this aspect of language with an emphasis on laboratory testing.Methods: This study was performed as a cross-sectional one. The participants included 134 male and female Farsi speaking individuals aging between 18-30 years. In this study two interrogative sentences with open and closed answers were used. The voice samples were analyzed by Dr.speech -real analysis software. Data analysis incorporated unilateral analysis of variance and an intonation curve was drawn for each sentence.Results: The parameter of duration among men and women was significantly different (p≤0.001). Duration in open questions was significantly longer than yes/no questions (p≤0.001). The intonation curve of the two groups were similar.Conclusion: Men and women use duration changes, for making difference in prosody. On the whole, duration among women is longer than men. In open questions, the duration of sentences is mostly due to the question word. The intonation curve in open questions has more amplitude. Women show much more changes in basic frequency for transferring interrogative state in their expressions.