The aim of this study was to evaluate the effects of LDL-based extenders in comparison with other media used for the refrigeration of canine semen: Tris egg yolk (EY), Equex(R), and INRA96(R). The test extender was composed of 6% LDL. The percentage of mobile spermatozoa after 4 days storage in a domestic refrigerator at +4 degrees C was 52.2%, 44.2%, 17.2%, and 24.5% for the 6% LDL, Tris Egg Yolk (20%), Equex(R), and INRA 96(R) extenders respectively for 100% of the dogs. After 7 days of storage, these percentages fell to 33.6%, 26.4%, 5.5%, and 14.8 % in the same extenders for 50% of the dogs. In vitro fertility tests were performed with the two extenders that gave the best mobility results, i.e. 6% LDL and Tris egg yolk (20%). These tests were conducted on the day of sampling (D0), 48 hours, and 96 hours after sampling. The results of the HOS test were 81.2% and 85.8% for egg yolk and 6% LDL respectively at D0, 74.1% and 78.5% two days later (D2), and 71% and 76.1% at D4. The results of the FITC/PSA test were as follows: 70.2% and 84.8% on D0, 69.3% and 84.2% on D2, and 59.6% and 73.7% on D4 for the EY and 6% LDL respectively. The acridine orange test was positive; in nearly 100% of cases none of the spermatozoa had been denatured on D0, D2, and D4. The 6% LDL extender was capable of preserving spermatozoa that had been stored in a domestic refrigerator at +4 degrees C for at least 4 days. This meant that the spermatozoa retained good cytoplasmic membrane integrity, had not capacitated, and contained intact DNA in comparison with the other extenders tested. The duration of storage is a very important consideration when faced with the problem of sending semen over ever-greater distances. Equex(R) and INRA 96(R) gave results that were 30% inferior; these extenders therefore seem ill-adapted for the refrigeration of canine sperm.