The nature of the oxygen contained in β-W was investigated withDSC, X-ray analysis on quenched samples and Auger spectroscope. It was shownthat the oxygen contained in nonpyrophoric β-W consists of the reversiblychemisorbed oxygen and the interstitial oxygen which could form an interstitialsolid solution with β-W. It seems better to consider β-W to be a metaphase of Wwith theinterstitial oxygen as stabilizer.