The oldest man alive according the the Guinness book of world records is Tomoji Tanabe, a Japanese man born on 18 September 1895, he is 113 years old.
The Guinness book just verified last month that the oldest living person alive is 115 year-old Edna Parker of the United States, who was born on April 20, 1893.
I found a few articles of people in other countries claiming to be the oldest person alive. One said that they were 138 years old, but Guinness couldn't confirm any of their claims. Apparently the 138 year old woman had changed her name once and didn't have an official birth certificate. If someone can seriously be 138 years old, then they couldn't have a mid life crisis until they're in their late 60's :)
I don't buy it though, that's just way too old.
Guinness book 09, 08