Abstract We have investigated the effect of the mitochondrial uncoupler carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP) on protein synthesis rate and initiation factor 2 (eIF2) phosphorylation in PC12 cells differentiated with nerve growth factor. FCCP treatment induced a very rapid 2-fold increase in intracellular Ca 2+ concentration that was accompanied by a strong protein synthesis rate inhibition (68%). The translation inhibition correlated with an increased phosphorylation of the α subunit of eIF2 (eIF2α) (25% vs. 7%, for FCCP-treated and control cells, respectively) and a 1.7-fold increase in the double-stranded RNA-dependent protein kinase activity. No changes in the PKR endoplasmic reticulum-related kinase or eIF2α phosphatase were found. Translational regulation may play a significant role in the process triggered by mitochondrial calcium mobilization.