The present invention relates to a method to identify one or more interference sources in a mobile radio system, preferably in a GSM radio network for mobile telephones. A received signal (r) consists of a wanted signal and a number of interference signals of which one is a dominating interference signal and where all signals includes a known training sequence (TK1,TK2, . . . ). The carrier is estimated and subtracted from the received signal (r) giving a remaining interference signal (s).This signal is correlated against known training sequences (TKj, j=0,1,2, . . . ,7) resulting in a training sequence associated with the interfering signal. According to the invention, the identification code (BCC) of a possible interference source (BS1) from said training sequence is determined. After that, a number of candidates (CA1,CA2, ), each corresponding with a certain cell from the identification code (BCC) are determined and also the frequency which is disturbed and the timing offset (t1,t2, . . . FIG. 7) for the frequencies used by said candidates. Finally it is investigated if one or more (fa,fb) of these have the same time offset as the interference signal (t0) resulting in that at least one candidate (CA3) with the best matching offsets on its frequencies is identified as the interference source.