The toxicity, accumulation, and elimination of diazinon were investigated for the european eel,Anguilla anguilla.The 24, 48, 72 and 96‐h median lethal concentrations (LC50) were 0.16, 0.11, 0.09 and 0.08 mg/L, respectively. Fish exposed to sublethal concentration (0.042 mg/L) accumulated diazinon in liver and muscle tissues. Bioconcentration factors (BCF) of diazinon were 1850 in liver, and 775 in muscle over the 96‐h exposure period. Upon removal from diazinon containing water the contaminated fish rapidly eliminated diazinon. The excretion rate constants of this insecticide were 0.108 h‐1for liver and 0.016 h‐1for muscle. Diazinon half‐lives were 16.6 and 33.2 hours for liver and muscle, respectively.