He worked for the Finance Ministry of the Estonian Soviet Republic until 1979, and later headed the state savings bank.
From the very creation of the Reform Party in 1994, Kallas has been its chairman.
From 1991 to 1995, he headed the Bank of Estonia before a brief spell as foreign minister to 1996. He was an MP from 1995 to 1999 and has served as finance minister under Mart Laar since 1999.
He speaks and writes English, Finnish and Russian. His wife Kristi is a doctor, his son Ulo works for Hansapank, and his daughter Kaja recently graduated from Tartu University's faculty of law.
The new prime minister spends his spare time playing tennis and riding bikes, reading about history and international relations, and going to the theater. He is also president of the Estonian Cyclists' Association.