Cellular replacement offers the potential of a `cure` for type 1 diabetes mellitus. Shortage of suitable donors limits widespread implementation of this approach. Recent research has been focused on potential new sources of beta-cells including embryonic and adult stem cells, and other organs cells. The contribution of beta-cell replication to new islet formation, in addition to the potential for transdifferentiation of pancreatic acini and ductal cells in adult human pancreas is not clear. The existence of true stem cells within pancreas remains contentious issue. In this review, we summarized the possible sources of new insulin-secreting cells.