Several analytical methods for the residue analysis of musk xylene (MX), musk ketone (MK), and other nitro musks in fish are presented and discussed. In particular because of a publication about a fast and simple analysis without any clean-up procedure, the necessity of a thorough clean-up of fat-containing samples is emphasized. In addition, the present knowledge about the high bioconcentration of these lipophilic pollutants in fish is summarized. In a long-term bioconcentration study we found in rainbow trouts bioconcentration factors (BCF) on a wet weight basis (BCFW) of MX from 4,200 to 5,100 while the BCF values on a lipid basis (BCFL) ranged from 115,000 to 122,000. These BCF values of MX are in good agreement with the BCF values calculated from the n-octanol/water partition coefficient (log K-ow = 4.90) using the Quantitative Structure-Activity Relationship (QSAR). A published study with extremely low bioconcentration factors of MX is critically discussed. (C) 1997 Elsevier Science Ltd.