The Principality of Andorra is a small European state located in the central Pyrenees. Since the Middle Ages, it has retained political independence from its two neighbouring countries, France and Spain. Until recently, Andorra maintained a relative stable population and was dependent upon agriculture and livestock. Since 1940, however, a marked change in these conditions has given rise to an explosive increase in the size of the population and traditional systems of production have been replaced by tourism, commerce and service industries. These changes have influenced the model of nuptial seasonality. Based on data from 10,188 marriage certificates covering a period from 1606 to 1960, nuptial seasonality was assessed by estimating Henry's seasonality coefficient. Temporal and geographic changes in the seasonality model were assessed using linear regression analysis and analysis of variance. In addition, the Uh index--an estimate of the intensity of the seasonality model--is proposed to assess changes in the different seasonality models. The results indicate a relaxation of seasonality over time and in those parishes in which substantial demographic and socioeconomic change has occurred in recent years, suggesting a strong dependence of seasonality on the system of production.