Alastair Seeley fastest in three of the four classes
Hampshire's James Hillier top in Supertwins
Wet and windy conditions for first practice
Alastair Seeley, who scored a hat-trick of wins in 2012, has the overall record in his sights.
"We're hoping to get a dry run and put a good show on for everybody," says the 35-year-old from Carrickfergus.
Image source, Press EyeThe newcomers are now out on the circuit with a few spits of rain in the cold air.
Northern Ireland rider Glenn Irwin, a leading competitor in the British Supersport Championship, is among those sampling the action.
"There is a lot to learn about the wind at the North West 200," says Phillip McCallen. He should know - the BBC pundit holds the record of five wins in a day.
Image source, Press EyeRiders are advised about the conditions on the North West circuit
Let us know who you think will post the best qualifying time in Superbikes today by using the voting buttons on the right. The Ts and Cs are here
Voting closes at 11:15 BST.
Video streaming of today's practice session starts on the BBC Sport website at 10:00 BST, along with Radio Ulster's coverage which is on medium wave and the website.
Welcome to the 2015 North West 200 where it is overcast but, most importantly, dry. The riders will face windy conditions as they try to post competitive qualifying times. There is another practice session on Thursday but, with aggregate times counting, the riders need to be quick out of the blocks today.