Routine high latitude observations made in Antarctica form a climatological baseline of the ionosphere extending back to 1958 at Mawson and Casey, and for almost two decades at Davis and Macquarie Island. The ionosonde data collection program operates so that the ionosphere is sampled sufficiently often that changes can be unambiguously identified. Each data sample is called an ionogram and is ... the raw data collected by the ionosonde. Ionograms are reduced to a series of Internationally agreed tabulations. This process ensures the long-term integrity of the data set. The tabulated data are: fmin, foE, foF1, foF2, fxI, h'E, h'F, h'F2, M(3000)F2, foEs, fbEs, h'Es, type of Es. The scaling conventions ensure that these scaled values also contain additional information on radiowave scattering in the F region and the effects of absorption and interference using a range of descriptive and qualifying terms with the scaled values. The tabulated data are available from World Data Centers. Data tabulated prior to 1985 is available on the WDC CDROM of ionospheric data.