The Combined Defence Services Examination (I) is a national-level entrance test for Indian students who wish to join the Indian Military Academy, Naval Academy, Air Force Academy, or Officers' Training Academy. The examination assesses candidates' knowledge in English, General Knowledge, and Elementary Mathematics. Successful candidates are shortlisted for admission to the respective academies based on their performance and medical fitness. The examination is conducted by the Union Public Service Commission (UPSC) twice a year, typically in February and November.

Candidates must be unmarried Indian citizens. For the Indian Military Academy and Officers' Training Academy, a bachelor's degree from a recognized university is required. For the Naval Academy, a B.Sc. degree with Physics and Mathematics or a Bachelor of Engineering is necessary. For the Air Force Academy, a degree with Physics and Mathematics at the 10+2 level or a Bachelor of Engineering is mandatory. The age limit varies by academy but generally ranges from 19 to 24 years as of the examination date.

Applications must be submitted online through the UPSC website. Candidates need to register, fill in personal and academic details, upload required documents, and pay the application fee. A valid email ID and mobile number are essential for communication. After submission, candidates receive an e-admit card for the examination. Ensure all details are accurate to avoid disqualification.