Traditional underground wine cellars are a good example of bioclimatic construction, providing optimum conditions for maturing wine with no energy consumption. This article studies the annual thermal behaviour of traditional underground wine cellars in one of the most well-known wine producing areas in Spain, the Ribera del Duero. For this we have applied a method based on multiple regression analysis using experimental data monitored for 1 year. The results show that the interior air temperature is fundamentally conditioned by the undisturbed temperature of the ground at the average depth of the wine cellar and by the temperature of the outside air (R(2) varies between 0.937 and 0.974, with an average of 0.964 for the three wine cellars studied). However, the stability of the wine cellar during changes of outside temperature differs according to the time of year. In the spring and summer, the stability is excellent and the influence of the ground temperature is much greater than that of the outside air temperature (beta coefficient for the ground temperature is 0.85 compared to 0.17 for the outside air temperature). In the autumn and winter, the stability of the wine cellar is reduced by the increased ventilation, reducing the influence of the ground temperature (beta=0.70) and increasing that of the outside air (beta = 0.42). (C) 2009 Elsevier Ltd. All rights reserved.