I use hazard regression methods to examine how the age difference between spouses affects their survival. In many countries, the age difference between spouses at marriage has remained relativelystable for several decades. In Denmark, men are, on average, about three years older than the womenthey marry. Previous studies of the age gap between spouses with respect to mortality found that havinga younger spouse is benefi cial, while having an older spouse is detrimental for one?s own survival.Most of the observed effects could not be explained satisfactorily until now, mainly because of methodologicaldrawbacks and insuffi ciency of the data. The most common explanations refer to selectioneffects, caregiving in later life, and some positive psychological and sociological effects of having ayounger spouse. The present study extends earlier work by using longitudinal Danish register data thatinclude the entire history of key demographic events of the whole population from 1990 onward. Controllingfor confounding factors such as education and wealth, results suggest that having a youngerspouse is benefi cial for men but detrimental for women, while having an older spouse is detrimentalfor both sexes. (Author abstract)