Spent V catalyst was ground, classified, annealed at 1073 K for 21 h to remove S compds. and converted (10 g) to KVO(3) by reaction with KCl at 874 K for 1-3 h under steam How (53 g/h). The reaction was followed by adsorption of formed HCl in aq. NaOH soln. (argentometry). The reaction yields increased up to 99% with increasing reaction time. The highest yield of KVO(3) was achieved when 0.250-0.355 mm fraction of the spent catalyst was processed (KCl content up to 60% of the catalyst mass used).