Earnhardt, 42, was sidelined for the final 18 races of the 2016 season after suffering a concussion.
On Wednesday, he participated in an on-track testing session at Darlington Raceway under the supervision of Charlotte neurosurgeon Dr. Jerry Petty.
Earnhardt was cleared by Dr. Micky Collins, medical director of the UPMC Sports Medicine Concussion Program in Pittsburgh. Collins, who consulted with Dr. Petty following Wednesday's on-track activity, has overseen Earnhardt's rehabilitation program and also treated him for a similar injury in 2012.
"I expected things to go really well yesterday, and that’s exactly what happened," Earnhardt said of an afternoon spent behind the wheel at the 1.366-mile South Carolina track. "Actually getting in a race car was an important final step, and it gives me a ton of confidence going into 2017."
Earnhardt completed 185 laps in his No. 88 Chevrolet during the course of the nearly five-hour session. Crew chief Greg Ives was on hand to oversee his driver’s efforts as well.
Earnhardt, recently voted the series most popular driver for the 14th consecutive season, said he expects to do more testing in January "to help knock the rust off."
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"When it's time to go to Daytona, I'll be ready," the winner of 26 premier series races said.
The 2017 racing season officially gets underway with the 59th running of the Daytona 500, scheduled for Sunday, Feb. 26 (2 p.m. ET, FOX, MRN, SiriusXM NASCAR Radio).
Earnhardt will not compete in the annual non-points, season-opening race, The Clash at Daytona International Speedway (Feb. 18, 8 p.m. ET, FS1, MRN, SiriusXM NASCAR Radio). Instead, HMS officials said Alex Bowman, who filled in for Earnhardt in 10 of the final 18 races of 2016, will drive the team's No. 88 entry.
Bowman won the pole at Phoenix in November, his first in the series.
"Everyone agreed that he more than earned (the opportunity)," Earnhardt said, "and (sponsor) Nationwide was 100 percent on board."
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It's possible Earnhardt could participate in up to two additional tests – Hendrick Motorsports is one of four teams expected to take part in a Goodyear tire test scheduled for Jan. 10-11 at Las Vegas Motor Speedway, and the season's first organizational test is tentatively scheduled for Jan. 31/Feb. 1 at Phoenix International Raceway.
Collins called Earnhardt "one of the hardest-working patients I've ever encountered."
"He's done everything we've asked, and we believe he is ready to compete at a professional level again and can withstand the normal forces of a race car driver," Collins said. "Dale has been very open with us, and we've had plenty of time for his treatment, so we feel very good about his long-term prospects and how this has been managed by everyone involved."
Team owner Rick Hendrick said he's proud of Earnhardt "for listening to his body and standing up to take responsibility for his health.
"He's worked extremely hard and set a terrific example for others," Hendrick said. "It's great news as we go into the offseason, and we can't wait to see him back on the race track at Daytona."
In addition to Bowman, four-time series champion Jeff Gordon also drove for the team in eight starts during Earnhardt's absence.
Earnhardt was 13th in points with six top-five finishes before being sidelined prior to the July race at New Hampshire Motor Speedway and wound up 32nd in the final standings. The 2012 injury forced him to miss two races; he finished 12th in points that season.