The aim of cell-based therapies is to replace or repair damaged tissues and organs. A diverse number of disorders are amenable to this approach, including haematopoietic, neurological and cardiovascular diseases, as well as bone defects and diabetes. Central to the success of cell therapy is the necessity to be able to identify, select, expand and manipulate cells outside the body. Recent advances in adult stem cell technologies and basic biology have accelerated therapeutic opportunities aimed at eventual clinical applications. Adult stem cells with the ability to differentiate down multiple lineages are an attractive alternative to human embryonic stem cells (hES) in regenerative medicine. In many countries, present legislation surrounding hES cells makes their use problematic, and indeed the origin of hES cells may represent a controversial issue for many communities. However, adult stem cells are not subject to these issues. This review will therefore focus on adult stem cells. Based on their extensive differentiation potential and, in some cases, the relative ease of their isolation, adult stem cells are appropriate for clinical development. Recently, several observations suggest that multipotential adult stem cells are capable of producing a whole spectrum of cell types, regardless of whether or not these tissues are derived from same germ layer; highlighting the opportunity to manipulate stem cells for therapeutic use.