The objective was to investigate the effect of dry coating of salbutamol sulphate (SS) with magnesium stearate (MgSt) on the kinetics of powder de-agglomeration. The relative de-agglomeration of the MgSt coated SS powders was higher than uncoated SS at all air flow rates; the SS coated with 2 % MgSt showed the highest extent of de-agglomeration (> 5 % MgSt coated SS > 1 % MgSt coated SS). Rate of de-agglomeration was described by a cumulative de-agglomerated versus time profile. Profiles fitted a mono-exponential model and the de-agglomeration rate constant (k_d) was estimated. No significant differences existed between any of the uncoated and coated powders. The significance of this study relates to the improved aerosolization and de-agglomeration performance of the MgSt coated SS powders with optimum performance of 2 % MgSt coated SS. More significant is the finding that no change existed in de-agglomeration rate constants between the coated and uncoated powders, with the potential implications that their aerosol plume concentration and deposition patterns were similar.