The effects of doping and uniaxial stress on the structural and magnetic properties of VO2 are reviewed. Important electron-electron correlation effects are deduced : (i) in the metallic phase from the results obtained V1-xNbxO2 alloys, (ii) in the insulating phases of pure VO2 at ambiant pressure (M1), under uniaxial stress or in the presence of Cr impurities (T and M2)