Laboratory radiotracer experiments were performed to study the uptake, assimilation and retention of americium (241Am) and cesium (134Cs) by the common cuttlefish Sepia officinalis. Uptake and loss kinetics of the radionuclides were measured following exposure through sediments, seawater and food at different stages of the animal's life cycle. Sediment was found to be a minor uptake pathway for both radionuclides in juveniles. Following a short seawater exposure, cuttlefish accumulated 241Am and 134Cs, but only to a limited extent (whole-body CF < 2). Among the cuttlefish organs, branchial hearts and their appendages displayed the highest degree of uptake for 241Am (CF = 42 and 16, respectively), but these tissues contained low percentage of total 241Am due to their relatively small contribution to whole organism weight. The major fraction of incorporated radionuclides was associated with muscular tissues (viz. 65% and 82% of total 241Am and 134Cs, respectively). Wholebody loss of 241Am and 134Cs was relatively rapid (Tb¿ = 14 and 6 days, respectively). After dietary exposure, around 60% and 30% of ingested 241Am was assimilated into the tissues of juvenile and adult cuttlefish, respectively. However, assimilated 241Am was more strongly retained in adults than in juveniles (Tb¿ = 28 vs. 5 days, respectively), suggesting that different mechanisms govern 241Am elimination at both ages. Ingested 134Cs was assimilated to a similar extent in juveniles (29%) and adults (23%), but the depuration rate was four times faster in adults. Our results strongly suggest that these two radionuclides follow different excretion pathways and that the mechanisms can vary with age for a given radionuclide.