It is shown that Majorana neutrino's absolute mass scale measurement can in principle be carried out using intense \beta beams. This could be achieved by counting the lepton number violating events in a two step process: the nuclear decay in flight and the subsequent neutrino induced interaction. The relativistic boost results in the gain in the content of Majorana neutrino helicities responsible for the lepton number violation. A simple formula to calculate this gain is presented. Specific examples of the two step processes are indicated and relevant cross sections are given.

PACS numbers: 23.40.--s, 14.60.Pq, 23.40.Bw