The effects of temperature on the functional properties of some members of two solute carrier families were investigated using heterologous expression in Xenopus laevis oocytes and electrophysiology. The kinetic parameters were determined in a range of temperatures from 20 to 30°C. The rat GABA transporter GAT1, three different orthologs of the intestinal oligopeptide transporter PepT1 and the Manduca sexta neutral amino acid transporter KAAT1, have been considered in this studies. These transporters are derived from organisms with different thermal behaviour: GAT1 from the neurons of a homeotherm mammal, KAAT1 from the intestine of a poikilotherm invertebrate, PepT1 from epithelial tissues of two poikilotherm (seabass and zebrafish) and one homeotherm (rabbit) organism. Raising the temperature from 20° to 30°C causes changes in the electrophysiological behaviour. Transport-associated currents, presteady-state currents and substrate affinity were determined for each transporter at 20-25-30°C. In all cases higher temperatures increase Imax and cause a reduction in substrate affinity. On the contrary, the transport efficiency is differently affected : it is increased with temperature in PepT1, decreased in KAAT1, and unaltered in GAT1. The Q10 of the transport-associated currents, is in the order of 3 to 8 in GAT1, 3 to 4 in KAAT1 and 2 to 4 for PepT1, according to the membrane voltage. The transient currents from rabbit PepT1 and from GAT1 show a progressively faster decline as the temperature is increased from 20 to 30 °C, and they become similar to those of KAAT1 and fish PepT1s at room temperature. The amount of charged moved, plotted in the Q/V relationship, is shifted to negative potentials by higher temperatures. The substrate affinity varies differently in the rGAT1, msKAAT1 and rbPepT1, in relation to voltages and temperature, but the effects can be generalized in an increase in the K0.5 from 20° to 30°C. Comparison of the amino acidic sequence between the mammalian and fish orthologs of PepT1 highlights the residues that may be involved in temperature sensitivity. Preliminary results on the Q10 of transport currents show an increase of this parameter when the two charged residues present in fish are introduced in the rabbit transporter (Q188E and A196K, rabbit numbering). The results presented in this work underline the functional adaptation of transporters to temperature and suggest the presence of specific residues that establish the protein activity in relation to the thermal life condition of the organism.