The Indian Administrative Service examination is conducted by the UPSC, this examination has following two stages:

Preliminary
Mains

You need to choose one of following optional subjects in the Mains examination:

Agriculture
Animal Husbandry and Veterinary Science
Marathi
Philosophy
Kannada
Geography
Civil Engineering
Geology
English
Political Science
Essay
Sindhi
Botany
Malayalam
Persian
Bengali
Management
Punjabi
Economics
Electrical Engineering
Russian
Indian History
General Studies
Medical Science
Pali
Anthropology
Mathematics
French
Chemistry
Nepali
Tamil
Konkani
German
Public Administration
Law
Mechanical Engineering
Manipuri
Sociology
Commerce
Kashmiri
Urdu
Sanskrit
Chinese
Arabic
Oriya
Assamese
Zoology
Psychology
Hindi
Telugu
Gujarati
Physics
Statistics