The structure and stability of azido azacycloalkanes, N-n(N-3)(n), (n = 3-6), have been investigated at the B3LYP/cc-pvTZ level of density functional theory. The stability obeys the gauche effect. The most stable structure is N-5(N-3)(5) (7), while N-3(N-3)(3) (2) is the least stable structure. They are thermodynamically unstable towards dissociation into N-2. (c) 2005 Elsevier B.V. All rights reserved.