The objective of this thesis is to examine the seasonal birth pattern in Manitoba during the period 1920 to the present. First, a descriptive examination of the seasonal birth pattern from 1920 to 1985 is conducted. Second, the modern seasonal birth pattern is investigated by conducting questionnaire research on the reproductive behaviors and birth-month preferences of currently reproducing women in the city of Winnipeg. The findings indicate that the seasonal birth pattern in Manitoba has undergone considerable change during the period 1920-1985. These changes are linked to broad socio-economic and demographic changes within the province during this period. The questionnaire survey data suggest that the modern seasonal birth pattern is influenced to some extent by a group of seasonal birth planners within the currently reproducing population. To conclude, some directions for further research are suggested.