Several types of WLS fibres, candidates to be used in the TILECAL/ATLAS detector, were irradiated in a Co-60 gamma source TWO irradiations were performed with Bicron, Kuraray and Pol.Hi.Tech fibres: In the first one, the fibres were exposed to a total dose of 116 Krad (low dose irradiation). In the second one, the fibres were exposed to 693 Krad thigh dose irradiation). The degradation of light output was measured just after irradiation and followed during several days. The results are presented.