Abstract: The invention relates to a process for preparing caprolactam by admixture of cyclohexanone oxime to a reaction mixture comprising caprolactam and sulfuric acid using a mixing device, said mixing device comprising (i) a tube through which the reaction mixture can flow, and (ii) channels disposed around the tube, said channels opening into the tube, said process comprising: passing the reaction mixture through the tube, and feeding the cyclohexanone oxime into the reaction mixture through one or more of said channels, wherein Re>5000, Re being the Reynolds number as defined by ?·V·D/?, wherein ?=density (in kg/m3) of the reaction mixture that is fed to the tube V=velocity of the reaction mixture, V being defined as W/A, wherein W is the flow rate (in m3/s) of the reaction mixture that is fed into the tube and A is the cross section area of the tube (in m2) at the level where said channels open into the tube D=diameter of the tube at the level where said channels open into the tube (in m) ?=viscosity of th