The effect of temperature on the uptake kinetics of strontium (Sr) in the common carp (Cyprinus carpio) was studied in vivo, exposing pre-acclimated fish to a wide range of Sr concentrations in water (Sr t o t a l =0.2-10 000 μM; Ca t o t a l =348 μM) at 10, 20, 25 and 30 o C. Sr uptake rates were determined in the whole body, gills and blood of the fish after an exposure period of 3 h and were analyzed as a function of the free-ion activity of Sr and Ca in water. The uptake of Sr 2 + by the whole body, gills and blood increased with temperature and showed saturation kinetics with the increase of Sr 2 + activity. Analyzing the observed uptake rates with a Michaelis-Menten type model showed that the kinetic parameters (J m a x , K m and K i ) for both Sr 2 + and its analogue Ca 2 + are temperature dependent. Thermodynamic analysis of the temperature effects indicates that the Arrhenius activation energies (E a ) required for Sr 2 + uptake (91.9 kJ mol - 1 ) and Ca 2 + uptake (105.9 kJ mol - 1 ) in the whole body of carp were constant over the temperature range 10-25 o C and showed a break in the Arrhenius plots above this temperature. The Arrhenius plot for the Sr 2 + uptake in blood was similar to that for the whole body uptake with an E a of 98.1 kJ mol - 1 . However, the E a for Sr 2 + uptake in gills was much smaller and constant (58.1 kJ mol - 1 ) over the temperature range of 10-30 o C. For a temperature change from 10 to 25 o C, the Q 1 0 for Sr 2 + uptake in whole fish, gills and blood were 3.71, 2.29 and 4.05, respectively. Compared with Ca 2 + uptake, Sr 2 + uptake appears to require a lower activation energy for transport across the solution body interface in carp. The similar pattern of Arrhenius plots and magnitude of activation energies for Sr 2 + uptake both in blood and whole fish suggest that the uptake into the blood across the basolateral membrane is the rate-limiting energy barrier and hence dictates the overall uptake rate of Sr 2 + in whole fish.