PIP: The age/sex-specific mortality trends of France and Italy were studied over the 1899-1979 period in as much detail as possible in an effort to distinguish between cohort effects and those related to period changes. Complete series of mortality data by individual years of age and calendar years were available from 1869 to 1979 for Italy and from 1899 to 1982 for France. For both countries, these data include the military and civil deaths not registered in vital statistics during the war periods. They cover each national territory as defined by its present boundaries. The graphical representation method of mortality surfaces, elaborated by Vaupel, Gambill, and Yashin (1985), was adopted. The age/sex-specific mortality patterns of France and Italy have not followed the same trends, and the differences observed today are not those of 100 years ago. The mean death probabilities for the 1975-79 period were used to illustrate the age-specific patterns of mortality. Although infant mortality was higher in Italy than in France, the death probabilities at ages 1-15 for both sexes were roughly the same for both countries. At ages 15-23, they were much higher in France than in Italy, and they remained considerably higher in France up to age 55. From then on, the sexes differ: for males, the 2 countries showed similar patterns, whereas for females the probabilities were noticeably higher for France. The situation was very different for both countries at the beginning of the century. For both sexes, higher mortality was observed in Italy not only during infancy but throughout childhood and the adolescent years up to age 15. The 2 countries showed similar patterns from 15-25. Above age 25, the 2 countries had similar patterns for females, whereas male mortality was higher in France right up to the old age groups. Such differences in the age-specific mortality trends depend in part on a different development of health and social conditions but also may be due to factors concerning the history of particular groups of generations. The general health progress made in both countries has played an important role but, on the whole, a more favorable role in Italy. Italy's infant and child mortality have drawn nearer the French level, while it has increased its advantage regarding adult mortality. France has strengthened its position only at older ages. There have been many perturbations since 1900, the most important of which has been the 2 world wars. They affected the 2 countries differently both in terms of their immediate effects on both the civil and military populations and in the longterm effects on the cohorts that had suffered most. These cohort effects, largely related to World War I, seem to have disappeared at this time, most likely in part because of selection relevelling the chances of survival of the various cohorts and in part because of general health progress masking the slight differences that may remain.