Widening adult participation in higher education as part of the development of lifelong learning strategies has been promoted by the European Union since the 1990s. Only recently, the 2011 Council resolution on a renewed European agenda for adult learning underlined the need to encourage higher education institutions to embrace adult learners. The Bologna process has also emphasised the importance of ensuring access to higher education for adult learners (e.g. mature and non-traditional students) and that they be given appropriate support from the beginning. Along with the increasingly rapid technological change, globalisation, decreasing job tenure periods and demographic trends, the need to provide adults with possibilities to take their skills "one step up" has been put even higher on the political agenda. Opening up higher education to adult learners, especially those who have not been engaged in studies at that level before, is seen as crucial in this context. One of the headline targets of the European 2020 strategy is to boost the share of the population aged 30-34 having completed tertiary or equivalent education to 40 per cent by 2020. In spite of this, available statistical data reveal that actual developments of adult participation in higher education vary a lot between the countries in Europe. Particularly, the rates for mature students entering higher education aged 25 to 39 years have not developed uniformly across the European countries during the last decade. While in some countries (e.g. Austria, Czech Republic, Slovak Republic, Spain) participation rates have increased between 2000 and 2010, there is a decline in other countries (e.g. Finland, Norway, Sweden, Germany, the Netherlands, United Kingdom) during the same period. The decline recorded in the northern and western countries might be also due to a growing number of young people entering higher education directly on completion of secondary education. However, even in the countries where rates for mature students have increased, the highest rates did not exceed 20 per cent in 2010. In only a very few countries (e.g. Portugal, Iceland, Sweden) the rates for mature students were higher than 20 per cent in 2010. While the overall progress towards the 2020 benchmark on the 30-34-year-olds having completed tertiary education or equivalent education is promising (35.8% in 2012), provisions for adults more generally appear rather moderate. This in turn raises questions about what the relevant factors facilitating and inhibiting adult participation in higher education are, how higher education institutions might provide better for the needs of adults and what action can be taken at different levels in order to foster the process of opening higher education to adults.