Their choice is between Umno's Azahar Ibrahim, 39, a former assistant district officer or PAS' Normala Sudirman, 38, a former remedial teacher.
There are 12 polling districts, each with a polling station. Tenang, located in northern Johor, consists of three Felda settlements, five traditional Malay kampong, three Chinese new villages, 25 modern residential area, one government quarters, four Indian estates and two Orang Asli villages.
Voting is from 8am to 5pm. The vote counting will be done in each polling station soon after the polls are close. The ballot boxes will then be transferred to the main tally centre - Labis municipal hall - where the final result announced. The Election Commission expects the results to be known by 9 pm.
According to the weather broadcast, morning in Tenang will be chilly and cloudy, to be followed by heavy rain in the afternoon.
It has been raining all day long over the past few days, dampening the final leg of campaigning for the contesting political parties.
The Tenang state seat fell vacant on Jan 17 when the former assemblyperson Sulaiman Taha from Umno died due to complication of diabetes.
Tenang, one of the two state seats under Labis parliamentary seat, has always been a BN stronghold. BN won the seat in the 2004 general election with 5,517 majority but this was slashed to 2,492 in the 2008 general election.
For more read here
Live updates by the star, here