This chapter discusses Roman demography that can be approached in two ways. First, the population of the empire and of its regions can be examined for level, increase or decrease, age and sex structure, and so on. Second, population can be broken down into its three major demographic components: mortality; fertility; and migration. The pattern of Roman fertility was chiefly determined by two factors: marriage customs; and the methods by which fertility was controlled within the ancient world. The Roman demographic structure, though undeniably harsh by modern standards, posed no obstacle to modest population growth. Most of human history has been lived under conditions of mortality not unlike Rome's. Where peace, prosperity and freedom from general epidemic have obtained, populations of the past have normally experienced a modest measure of sustained growth; there is no reason to believe that the Roman empire's population did not grow similarly. The chapter hypothetically reconstructs the pattern of such growth in the early empire.