The ISO mission has shown the importance of establishing a reliable spectrophotometric calibration over the range of wavelengths covered by its multiple observing modes. We examine the needs for infrared calibration with the new generation of 8-10 metre class telescopes in the light of this experience, in particular the 10-m Gran Telescopio Canarias (GTC) that will enter operation in the Roque de los Muchachos Observatory, La Palma, Canary Islands in late 2003. Although our study is focussed towards mid-infrared calibration and, in particular, its mid-infrared Day 1 instrument, denominated CanariCam, it is also applicable to the near infrared. The state of infrared calibration is briefly examined, along with the problems of the currently available lists of calibrators. We demonstrate that the current calibration lists, particularly in the mid-infrared, are inadequate for reliable calibration of GTC observations and, by extension, observations with other telescopes of a similar diameter. Apart from a low density of stars on the sky, the majority of calibrators for 10 μm are almost 7 orders of magnitude brighter than the sources to be calibrated; we show why both of these factors may cause severe difficulties with data reduction if not remedied.