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The phase transition of VO2 was examined by the X-ray method for the single-crystal whiskers of VO2.00 and VO2.07. Attention was directed mainly towards the different behaviour in the different specimens at the premonitory stage of the monoclinic tetragonal transition. Appearance of a triclinic twin at this stage in VO2.07 indicated a larger degree of monoclinic distortion than in VO2.00.