A letter of intent (LOI) is a supplemental note applicants write to medical schools, residencies, and other medical programs to let faculty know of their interest in an institution and the distinctiveness of their candidacies. Letters of intent can be written early in an effort to obtain an interview, after the interview to show enthusiasm and remind the faculty of the candidate's worthiness, or after a wait list notification (for medical and dental students who don't participate in the Match).
The letter should be written in a timely fashion. In other words, there's no reason for a residency applicant to write a letter of intent in late February. The letter should avoid restating the strengths of the institution. Instead the applicant should express his/her interest and then move onto his/her strengths. An LOI should be a page or less.
For help writing a professional, expert LOI, contact me.