Laboratory experiments were carried out under environmentally realistic conditions in which Irish Sea sediment was resuspended into Irish Sea water for various time periods. In all cases, there was a significant (p generally < 0.05) increase in the dissolved (< 0.22 μm) activity concentrations of 238Pu, 239,240Pu and 241Am after mixing with the Irish Sea sediment. Dissolved Pu concentrations continued to increase throughout the maximum period employed (168 h), whereas dissolved Am concentrations showed no significant variation after the first sampling interval (24 h). The presence of 0.5 mg l−1 sodium dibutylphosphate had no effect on the remobilization of Pu but appeared to produce a small increase in the dissolved 241Am concentration (i.e. a 25%, 0.35 mBq l−1 increase). This was probably due to the solution complexation of Am by dibutylphosphate. In context, the increase is too small to have any likely environmental importance.