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Introduction: Recent industrial developments in human societies have caused rapid advancements in technologies of production and distribution of electricity, which in turn result in enhancement of power networks and utilization of high voltages. These networks and the high voltages in transfer lines cause the exposure to electric and magnetic fields. In this study, the situation regarding the magnetic fields from high-voltage (230 kV) substations in Tehran was investigated. Material and Methods: In this study, 8 high-voltage (230 kV) substations were selected (Shous, Shahid Firouzi, Ozgol, Kan, Tehranpars, Azadegan, Ghorkhane and Besat substations). The premises of each substation was divided into some stations and measurements were done in each one. Measurements were done according to the IEEE std 644-1994 Standard in a way that the device, specifically its probe, was kept at a height of 1 meter above the ground surface. Then, we tried to examine the probable effects of exposure to magnetic fields through the Essex questionnaire, with Cronbach coefficient of 94%, completed by the employees of the substations. These questionnaires were completed by substation operators as an exposed group (36 persons) and the employees of the office section of the Tehran regional electric company as a witness group (32 persons). Results: The measured density in none of the stations exceeded the standard limits of the International Commission on Non-Ionizing Radiation Protection. With regard to the questionnaire results about mental and neurological, cardiac and respiratory, and gastrointestinal and auditory disorders, we observed significant differences between witness and exposed groups, however, regarding skin allergies, there was no significant difference. Conclusion: Among all control rooms, the highest measured magnetic field was 6.9 mG in the Ozgol Substation Control Room and the lowest was 2 mG in the post of Shahid Firouzi. The control room of Ozgol substation is located on the second floor and bus-bars are located at a short distance from the eastern window, so the highest recorded magnetic field was measured in that control room. Among all switchgear parts, the highest field of 91.5 mG was measured in the Kan substation. In spite of accordance of the magnetic fields with the standards (based on measurements), it can be seen that exposure to magnetic fields at high-voltage (230 kV) substations causes the intensification of neurological and mental, cardiac and respiratory, gastrointestinal and auditory disorders but it has no effect on skin allergies.