The discarded houses of appendicularians can be important components of marine snow and might therefore be instrumental in mediating the vertical flux of metals from surface waters in oceanic ecosystems. Their significance in this regard depends on the retention of metals in these organic debris. To assess this, an experiment was conducted in which the release of cadmium and zinc from discarded houses of the appendicularian Oikopleura longicauda was studied using gamma-emitting radiotracers. The retention curves of the two metals conformed with a single exponential decay loss model. The retention half-times were of the order of two days, suggesting that sinking appendicularian houses would not transport these metals to deep ocean waters but could contribute to their flux out of surface waters.