In this research entitled noise standards for passenger cars in Iran, in order to identify the permissible levels of sound for passing-by noise and the noise from vehicle exhausts and horns, through a step processing method, at first the real current situation of vehicles was obtained through different tests carried out on 100 vehicles of different types. The results have been analyzed statistically using the ATATGRAPHICS PLUS Version 2.1 software. The second step has been the study of other countries’ standards and regulations as well as the European Commission Directives 70/15/EEC and 70/388/EEC which have formed the basis of this study. According to the test results analysed and the Directives mentioned above, the permissible sound levels that have been identified are as follows : 77 dB (A) for passing-by noise of the M1 class; 80 dB (A) for the N1class ; 86 dB (A) for exhaust noise and 87 dB(A) TO 112 dB(A) for horn noise for all types of vehicle .