North Korea's nuclear test in October 2006 came as a stark reminder that the problem of nuclear proliferation is alive and well and that the global nuclear arms control and non-proliferation regime is fighting for its survival. From Iran and North Korea to the nuclear black-market of A.Q. Khan, new challenges have been emerging virtually every other day and threatening to undermine the global arms control architecture. In the immediate aftermath of the end of the Cold War, nuclear proliferation was considered by many as a problem of the past. But the trends did not turn out as expected. India and Pakistan went nuclear in 1998 and opened a pandora's box. Nuclear proliferation, however, has tended to remain confined to three regions of the world in the post Cold War era: South Asia, Middle East, and East Asia. These are the region where states are locked up in intense regional rivalries. India and Pakistan seem perpetually on the brink of a war. India and China continue to have broadly conflictual relationship. Israel's conflict with its Arab neighbors seems to have no end in sight. The Korean peninsula continues to sit on the brink of a rivalry that did not end with the armistice in 1950. This dissertation looks at two of these regions, South Asia and Middle East, and examines the drivers of nuclear proliferation in so far as the key states in the region are concerned. It examines the role that the rivalries that states in these regions have with their neighbors have played in the spread of nuclear weapons in the region. The basic thesis is that the states in South Asia and Middle East have acquired or sought to acquire nuclear weapons for traditional national security reasons. But the dissertation goes further in exploring the role that the regional conflicts have played in shaping the basic security imperative of the states in the region.