Incoherent scatter radars are used principally to measure “power profiles” (total power versus range) from which electron concentration is inferred. When applied to the ionosphere D region this measurement is, due to very small signal-to-noise ratios and the range involved, especially susceptable to aircraft and meteor returns and to interference from other radars. We report a power spectrum based interference detection scheme which allows correction of the power profile. The power spectrum used is formed from the same data sequence used to form the power profile. This scheme has been successfully applied to Arecibo D region data.