The party was leading in 53 of the 80 seats while the SP-BSP-RLD alliance, which was said to emerge as a major force, was forging ahead in 25 seats.
The Congress was leading in just one seat Rae Bareli, where UPA Chairperson Sonia Gandhi contested. In Amethi, BJP's Union Minister Smriti Irani had overtaken Congress President Rahul Gandhi.
The prominent BJP candidates leading in their constituencies in Uttar Pradesh include Union Home Minister Rajnath Singh in Lucknow, Varun Gandhi in Pilibhit, Union Minister Mahesh Sharma in Gautam Buddh Nagar, Pravin Nishad in Sant Kabir Nagar, Hema Malini in Mathura, Sakshi Maharaj in Unnao and Ramapati Ram Tripathi in Deoria.
Bhojpuri star Ravi Kishan had established a lead of over 50,000 votes over his nearest rival, Ram Bhual Nishad of Samajadwai Party, in Gorakhpur.
State BJP President Mahendra Nath Pandey, who was trailing in the first three rounds, recovered lost ground and was leading in his constituency Chandauli.
A major upset for the BJP, however, is Ghazipur where Union Minister Manoj Sinha was trailing behind BSP's Afzal Ansari.
For the SP-BSP-RLD alliance, the election trends have brought bad news.
The BSP is leading in 15 seats and the Samajwadi Party in 10. The alliance has apparently failed to work out the caste arithmetic on the ground.
Samajwadi President Akhilesh Yadav is leading in Azamgarh by 4,234 votes over his nearest rival Bhojpuri star Dinesh Lal Yadav Nirahua.
His wife Dimple Yadav, after trailing in the early rounds, was now leading in Kannauj and party patriarch Mulayam Singh Yadav was leading in Mainpuri.
SP leader Mohd Azam Khan was leading in Rampur where his rival is Jaya Prada of BJP.
A major upset for the SP is Badaun where Dharmendra Yadav was trailing behind BJP's Sanghmitra Maurya.
( With inputs from IANS )