When Gautama was 29 years old, he discovered there was much suffering in the world around him. Traditionally it is explained that he suddenly recognised the problems of sickness, old age and death when visiting the city. Being shocked by the suffering of all living beings, he decided to search for way to end it. He left his wife and child, the palace and even his royal clothes, and started out on a spiritual quest.
http://viewonbuddhism.org/resources/index.html