Aphid parasitoids, Aphidius rhopalosiphi (De Stefani-Peres), were submitted during their larval development at three periods in autumn to natural winter conditions. Mummies were then exposed for one to five weeks at 0[degree]C and their cold tolerance was assessed. We measured the percentage of emergence, percentage of male and female sterility, female fecundity and temperatures of crystallization (Tc). Our first results show that there is a good emergence at 20[degree]C (>80%) for adults that were previously acclimated at the beginning of October and November, after one week as well as five weeks of cold storage. At the end of October, results were less satisfactory. Nevertheless emerged parasitoids sex ratio was high without any dependence to the acclimation period. Male sterility was always important and results in majority on a male offspring. Yet, female sterility was smaller but their 24h fecundity was low with exception for those that were acclimated at the beginning of November with a 9 or 14h light period. They presented a fecundity close to the laboratory ones that were reared at 20[degree]C and 16h light. Tc were measured for each period of acclimation and cold exposition. Results fluctuated around -25[degree]C and were not different one from the other whatever the acclimation period or the exposition time was. none