The two factors of live births and migration constitute the major determinants of the size and composition of the population for the provinces as well as for Canada as a whole. The decline in fertility has almost exactly offset the increase in the number of young women in the child-bearing age groups. The effective length of the reproductive period for women seems to have been cut almost in half during this century. Women in their mid-thirties and over have completed their families, and the younger women are in recent years apparently delaying family formation. Interprovincial migration within the last 25 years has resulted in heavy losses for Nova Scotia, Quebec, Manitoba, and Saskatchewan, and substantial gains for British Columbia, Ontario, and Alberta. Immigration seems to be declining very little. One must project for Canada continued moderate declines in fertility for a decade, to a point well below the replacement level, followed by a period of indeterminate duration (probably well beyond the year 2000) of a constant level of low fertility. (Author/MLF)