The seasonality of the real-estate market is a recognized phenomenon although little studied, notably in its relation with the real-estate cycle. By using a database on the real-estate transactions of the city of Bordeaux, we investigate here the links between the movements of the cycle and the modifications of the seasonality of the prices, for the whole market and by type of possessions. This descriptive approach allows to put the bases of a more relevant modelling of the prices series. On all transactions of the Bordeaux market (more than 170000 sales from 1985 to 2005), we obtain two main results. First, the amplitude of seasonality is related to the market growth rate. In addition, each break in trend prices implies a period of arrhythmia whose duration is proportional to the magnitude of the break. Secondly, these statistical relationships are specific to each type of surface. In conclusion, the local nature of the study should be extended to check the robustness and possibly refine the methods used.