The lactic acid bacterium, Lactococcus lactis subsp. lactis IL1403 was subjected to different cold temperatures for various times. Physiological experiments showed that this strain had an improved survival capacity in stationary phase as the temperature decreased. Two-dimensional electrophoresis of proteins extracted from cold-temperature exposed cultures showed that a dozen proteins are overexpressed up to threefold compared with exposure at 30 degrees C. Most of these proteins are overexpressed first, temporarily and second, in the first 10 h after the transfer to 8 degrees C. These observations indicate that response to cold stress in L. lactis subsp. lactis is an active phenomenon.