Islam is the fastest growing and the second largest religion in the world.

Among every four humans in the world, one of them is Muslim. Muslims have increased by over 235 percent in the last fifty years up to nearly 1.6 billion. By comparison, Christians have increased by 47 percent, Hinduism by 117 percent, and Buddhism by 63 percent. Islam is the second largest religious group in France, Great Britain and USA.

Islam is the fastest growing and the second largest religion in the world.
Source: http://islamicweb.com/begin/results.htm