The Rajya Sabha (first constituted in 1952) is a continuing chamber, that is, it is a permanent body and not subject to dissolution. However, one-third of its members retire every second year. Their seats are filled up by fresh elections and presidential nominations at the beginning of every third year. The retiring members are eligible for re-election and renomination any number of times. The Constitution has not fixed the term of office of members of the Rajya Sabha and left it to the Parliament. Accordingly, the Parliament in the Representation of the People Act (1951) provided that the term of office of a member of the Rajya Sabha shall be six years.

Source: ForumIAS