If I am not mistaken, you can but you'd have to complete your ADSO in your first residency before you can go for a second one. When my wife was an AF anesthesia resident and there were several LTC who had primary residencies in IM or FP doing residency again. For HPSP folks this is doable if they did a short residency (IM, FP, Peds) and only have 3-4 years after training to reapply. However, an USUHS grad who does general surgery (5-7 years depending on research or a utilization tour after internship) plus 7 years after training, they'd be doing another residency at 12-14 years later.