RESUMEN
Knowledge of the seasonal variation in births and deaths during normal years is important for analyses of the effects of wars, famines, epidemics or similar privations on these variables. In studies of seasonality, multiple trigonometric regression models are more flexible than the simple sine curve. The seasonal variation in mortality in Iceland, 1856-1990, shows a strong secular decrease, and a connection between this and the epidemiological transition is considered. Comparisons with findings in other European countries are made. The temporal trends in Iceland of the birth components; the twinning rate, the still birth rate and the secondary sex ratio, are presented and compared with the corresponding values in neighbouring countries. No marked differences were emerged.