Gilthead sea bream larvae (Sparus aurata) aged 47 days post hatching (dph) (11. 6-12. 8 mg in wet weight) were exposed to several sublethal concentrations of Cd2+ (0. 1, 5 and 10 mg/L) during 6 days in order to investigate the effects of this heavy metal on the expression of selected genes involved in detoxification (metallothionein-mt, glutathione peroxidase 1-gpx1), stress response (heat shock protein 70-hsp70, tumour necrosis factor α-tnfα) and ossification (osteocalcin-oc) processes. For this purpose, specimens of 47 dph were exposed first for 72 h from 0. 1 to 20 mg/L of Cd2+ in order to evaluate the median lethal concentration (LC50) for this metal, which was determined at 15. 32 mg/L. Considering the results regarding the relative transcript levels of gpx1 and hsp70, Cd2+ at any of the tested levels (0. 1, 5 and 10 mg/L) did not induce oxidative stress in gilthead sea bream larvae, whereas relative transcript levels of mt were increased at 5 and 10 mg/L of Cd2+ probably to detoxify this metal excess. Relative transcript levels of tnfα were not level dependent and were down-regulated in larvae exposed to 5 and 10 mg/L of Cd2+. At those concentrations, transcript levels of oc were down-regulated suggesting a disruption in bone mineralization. Results from this study provided insights in some molecular mechanisms underlying Cd2+-induced toxicity in fish at early stages of development. This is the first study to show that cadmium contamination can depress oc expression in teleosts. © 2012 Springer Science+Business Media Dordrecht.