The ruling BJP was ahead in two assembly constituencies, while the Congress, Samajwadi Party and the Bahujan Samaj Party were leading in three other seats, as per trends from five of the 11 constituencies.
Counting of votes began amid tight secuity on Thursday morning and the results were expected by evening.
Of the 11 seats where bypolls were held, eight were held by the BJP and one by its ally Apna Dal (Sonelal). Two other seats were shared by the Samajwadi Party and the Bahujan Samaj Party.
The Ghosi seat fell vacant following the resignation of sitting MLA Phagu Chauhan after he was appointed as Bihar governor.
On Monday, 47.05 per cent voters had exercised their franchise in the bypolls, mostly necessitated after sitting legislators got elected to the Lok Sabha in May.
According to the office of the state chief electoral officer, 109 candidates are in the fray for the bypolls to the assembly seats of Gangoh, Rampur, Iglas (SC), Lucknow Cantonment, Govind Nagar, Manikpur, Pratapgarh, Zaidpur (SC), Jalalpur, Balha (SC) and Ghosi.