The behaviour of Kr atoms implanted into aluminium at room temperature with a dose of 1×10 15 Kr/ cm 2 has been investigated by a channelling method for isochronal annealing up to 683 K. In the as-implanted state the Kr atoms are distributed over tetrahedral (T), octahedral (O), substitutional (S) and random (R) sites. On annealing at 433 and 593 K, the T- and O-site occupancies disappear, respectively, and in both cases the fraction of the S-site occupancy decreases and that of the R-site occupancy increases. The T- and O-site occupancies have been interpreted to be a result of the formation of Kr-vacancy (V) complexes of KrV 4 and KrV 6 , respectively, and the R-site occupancy to be Kr atoms associated with cavities. Therefore, the annealing stages at 433 and 593 K are explained in terms of the dissociation of KrV 4 and KrV 6 , respectively. On annealing at 683 K, solid krypton is formed.