of the acanthocephalan Paratenuisentis ambjguus and the nematode Anguillicola crassus were collected from eels from the river Weser, Germany, and examined for lead levels. In addition to these parasites, different fish tissues (liver, bile and intestine) were also analysed for lead, using electrothermal atomic absorption spectrometry. P ambiguus was found to contain the highest amounts of lead. The mean lead level in A. crassus was much lower, resembling the values obtained from eel tissues. The accumulation capacity of P. ambiguus was about 100 times higher than that of A. crassus. Thus, P. ambiguus can be considered a rather sensitive indicator of lead in aquatic ecosystems.