A rapid and simple HPLC-DAD method has been successfully developed to determine the sum of MG and LMG in rainbow trout muscle. It is based on the in situ conversion of LMG to MG using the oxidizing agent DDQ. The method was validated according to the criteria described in Commission Decision 2002/657/EC. The ob-tained recovery and precision values indicate the reliability of the proposed method. The CCa and CCb for MG were below the MRPL of 2 mg/kg. The proposed method was used to determine the MG residues in rainbow trout muscle samples (n ¼ 144) obtained from trout farms in Iran. The results showed that 48.6% of the samples contained MG residues, ranging between 0.30 and 146.1 mg/kg.Since this study is limited to farmed rainbow trout, further in-vestigations should be carried out to determine the MG residues in
other farmed fish species.