An estimated 68 percent of the 18 million eligible to vote in the first phase exercised their franchise by end of balloting at 5 p.m. in 87 of the 182 assembly constituencies, the Election Commission said.
It was the highest voting percentage since 61.54 percent of the electorate voted in 2002. This slid to 59.77 percent in 2007. Earlier, 59.30 percent had voted in 1998.
In New Delhi, the Election Commission said the nine-hour polling was "totally peaceful and historic".
Both the ruling Bharatiya Janata Party (BJP) and the Congress have asserted they will win but the election is widely seen as a referendum on Modi's 11 years of controversial rule.
The third major player is the Gujarat Parivartan Party (GPP) of former chief minister Keshubhai Patel, who parted ways with the BJP after giving up the chief minister's chair to Modi in 2001.
The BJP has fielded candidates in all 87 seats, the Congress in 84, GPP in 83 and the Bahujan Samaj Party in 79.
Queues began forming outside many polling booths even before balloting started at 8 a.m. Within three hours, 18 percent had voted. The numbers kept rising amid pleasant weather.
Fifty-four of the 87 constituencies voting Thursday lie in Saurashtra, Keshubhai Patel's known stronghold, and 33 in south Gujarat. BJP officials say the Keshubhai factor will not affect them majorly.
There were 846 candidates in the fray, including 46 women.
Ahmed Patel, political secretary to Congress president Sonia Gandhi, said after casting his ballot that the heavy polling "shows how much dissatisfaction is there among the people (against Modi)".
Amid media glare, Keshubhai Patel voted in Rajkot. Gujarat Congress chief Arjun Modhwadia exercised his franchise in Porbandar.
After casting his ballot, BJP state leader R.C. Faldu thundered: "We will win with a big majority."
Election Commission officials said polling took place peacefully all over the state.
The largest constituency by area was Abdasa (6,278 sq km) and the largest constituency by population Kamrej (304,621 voters).
At Maninagar in Ahmedabad, Modi was pitted against suspended police officer Sanjiv Bhatt's wife Shweta.
A possible victory for the BJP will be widely seen as a personal triumph for Modi, who towers over the party in Gujarat.
And with the next Lok Sabha election due in 2014, it could propel him to play a larger national role for the BJP.
If the BJP loses, the claims of Modi's political invincibility by his admirers would be punctured.