Large-eddy simulations (LES) of transition to turbulence in a horizontal annular cavity are performed, using a dynamic sub-grid scale model and second order schemes for time and space discretizations. Solutions for Prandtl number of 0.707 and Rayleigh number up to 7.5 x 10(5) are obtained. The onset of transition to turbulence and turbulence regimes are pointed out, as well as the dynamic characteristics of the thermal plume transition. The instantaneous and time average behavior of the flows, related to the velocity and temperature fields, are analyzed and compared with numerical and experimental results from other authors. The influence of transitional and turbulent flows on local and mean Nusselt number are also investigated. (c) 2007 Elsevier Ltd. All rights reserved.