Secondary analysis of the UK's 2011/12 Destinations of Leavers from Higher Education survey reveals that many existing assumptions about graduate internships are questionable. This article proposes a reliable way of estimating the true extent of internships including those reported as 'voluntary' jobs: hidden internships. In doing so the article finds: 1) At six months after graduation, internships are a small feature of the UK graduate labour market, but significant in certain sectors; 2) Unpaid internships are much more prevalent than previously estimated, especially in these same sectors; and 3) Contrary to some public policy debate, unpaid internships appear, on balance, to be a residual option more likely to lead to underemployment and less favourable career development outcomes. Post-graduation internships appear less likely than pre-graduation work experiences to confer long-term employability advantages.