Low fertility in most developed countries has prompted policy concern in relation to labour market supply, pensions, and expenditure on health and welfare services as well as policy debate about both the cost of children and the opportunity costs of parenthood. The extent to which family policy interventions can be effective in slowing or reversing fertility decline is much debated. This paper, based on a fertility module of the Scottish Social Attitudes Survey 2005, examines the current fertility, and ideal and expected fertility of a nationally representative sample of 455 parents of reproductive age and focuses on whether they plan to have another child. It compares the characteristics of those who intend to have another child with those who do not, and how parents with one child differ from those with more children. It addresses three questions about family size: (1) fertility ideals, (2) resources and the economic implications of childbearing, and (3) opportunities for childbearing and the effects of a late start on fertility expectations. It concludes that, despite a sustained period of low fertility in Scotland, childbearing ideals are robust and explanations of low fertility must derive from difficulties in realising those ideals. Difficulties in realising fertility aspirations are associated less with resources than with opportunities for childbearing, especially the timing of first birth. Those who delay their first birth are less likely to realise their ideal family size, and their lower fertility is associated with the opportunity costs of childbearing in terms of foregone qualifications, careers and earnings.