The Main Exam, or simply the 'Mains', is the second stage of the CSE. This is the most crucial and relatively the most toughest stage of all. The qualified candidates of CSAT are eligible for appearing in this exam.
The final ranking and selection for the Personality Test (Interview) depends on one's performance in this stage. The number of candidates to be admitted to the Mains is about 12 to 13 times the vacancies to be filled in a particular year.
The main examination is intended to assess the overall intellectual traits and depth of understanding of candidates, rather than the range of their information and memory.
The scope of syllabus for the optional subject papers is broadly of the honours degree level, which is higher than the bachelor's degree but lower than the master's degree. In case of Engineering and Law, the questions would be at the bachelor's level

It is a conventional essay-type written examination and consists of nine papers, each of three hours. All question papers other than language papers will be set both in english and hindi.

Paper I Indian Language: One can select it from the languages included in the Eighth Schedule of Constitution of India.
Matriculation standard;
Qualifying nature; the marks scored will not be counted for ranking.

Paper II English: Matriculation Standard. Qualifying nature; marks scored will not be counted for ranking.

Paper III Essay: One essay of 200 marks.

Papers IV & V General Studies: 300 x 2 = 600 marks

Papers VI, VII, VIII & IX: Two papers each of two Optional Subjects. 300 x 4 = 1200 marks.

Total marks of seven papers = 2000 marks.
Interview = 300 marks.
Grand Total marks for ranking = 2300 marks.

Two optional subjects can be choosen from 25 subjects, and the literature of one of the 30 specified languages. The subjects we choose need not be from what we have studied in college.

Optional Subjects:
*. Agriculture
*. Animal Husbandry and Veterinary Science
*. Anthropology
*. Botany
*. Chemistry
*. Civil Engineering
*. Commerce and Accountancy
*. Economics
*. Electrical Engineering
*. Geography
*. Geology
*. Indian History
*. Law
*. Management
*. Mathematics
*. Mechanical Engineering
*. Medical Science
*. Philosophy
*. Physics
*. Political Science and International Relations
*. Psychology
*. Public Administration
*. Sociology
*. Statistics
*. Zoology

Literature:
*. Arabic
*. Assamese
*. Bengali
*. Bodo
*. Chinese
*. Dogri
*. English
*. French
*. German
*. Gujarati
*. Hindi
*. Kannada
*. Kashmiri
*. Konkani
*. Maithili
*. Malayalam
*. Manipuri
*. Marathi
*. Nepali
*. Oriya
*. Pali
*. Persian
*. Punjabi
*. Russian
*. Sanskrit
*. Santali
*. Sindhi
*. Tamil
*. Telugu
*. Urdu

Combinations not allowed:

*. Political Science & International relations and Pubilc Administration
*. Commerce & Accountancy and Management
*. Anthropopgy and Sociology
*. Mathematics and Statistice
*. Agriculture and Animal Husbandry & Veterinary Science
*. Management and Public Administration
*. Any two branches of engineering
*. Animal Husbandry & VeterinaryScience and Medical Science
*. Combination of two Literatures.