Numerical and experimental study on steady mixed convection gas flow around a hot spherical particle is presented for small values of Reynolds and Grashof numbers and all mixed convection parameter range. The flow regimes considered are the axis-symmetric co-flow and opposed flow for the non-dimensional Boussinesq model. The sensitivity of the numerical computations with respect to the dimension of the computational domain is discussed. The opposed flow regime and the formation of re-circulation secondary flow is analyzed. A qualitative expression for the drag force induced on the particle by the flow is given for all range of the mixed convection parameter, the expression holds for the co-flow configuration but brakes up in the opposed flow regime when re-circulation secondary flow evolves. Experimental measurements of the drag force induced on a small spherical particle allows further examination of the numerical computations and theory. (c) 2004 Elsevier Ltd. All rights reserved.