As many as 8.95 lakh people are eligible to cast their votes at 961 polling stations in Nasirabad, Weir, Surajgarh and Kota South.
A total of 23 candidates are in the fray, with maximum of nine candidates contesting from Surajgarh and the minimum of three from Weir.
The by-elections were necessitated as BJP legislators Sanwar Lal Jat from Nasirabad, Bahadur Singh Koli from Weir, Santosh Ahlawat from Surajgarh and Om Birla from Kota South got elected to the Lok Sabha.
The main fight is between the Congress and the ruling Bharatiya Janata Party (BJP).
The counting of votes will take place on Sept 16.