This paper examines the relationship between fertility intentions and fertility behavior using the data from the National Survey of Families and Households with a sample of 2812 non-Hispanic Whites. Results demonstrated a strong relationship between fertility intentions and the percentage of having a birth. It was also noted that the effect on fertility is greater when the intentions are held with greater certainty. Furthermore fertility intentions and their certainty predict fertility behavior better among married persons as compared to all other variables in the model. Thus marital status is an important life course variable wherein a change in marital status significantly affects birth probabilities. Finally this study indicated that fertility is a purposive behavior that is based on intentions applied into the life course and changed when unexpected developments occur.