As many as 38 candidates are in the fray for the parliamentary seats – Kangra, Mandi, Hamirpur and Shimla.
The main contenders include Shanta Kumar of the Bharatiya Janata Party in Kangra and Congress candidate Pratibha Singh from Mandi.
Incumbent BJP MPs from Hamirpur and Shimla, Anurag Singh Thakur and Virender Kashyap, are re-contesting from their respective constituencies.
In the 2009 Lok Sabha election, the BJP had won three seats, while Congress leader Virbhadra Singh had won the Mandi seat.
Virbhadra Singh surrendered the seat in 2012 when he became the chief minister and his wife Pratibha Singh was elected as an MP in the by-poll.
Polling is being held at 7,382 polling stations.
Over 4.8 million electors are eligible to vote.