AbstractThe diagnostic problem of measuring electron temperature fluctuations with a relative level below 1% is outlined. It is shown that correlation radiometry of electron cyclotron emission provides sufficient sensitivity to overcome the limit set by intensity fluctuations of thermal radiation. The experimental set-up used for the first measurements is described and the first results obtained at the W7-AS stellarator are presented. With an extended arrangement a first comparison between the two different correlation schemes as developed at W7-AS and at TEXT became possible.