Fears are mounting for a missing 33-year-old autistic man, who ran away from his 24-hour caregiver on Friday afternoon.

Nigel Peterson was last seen getting out of his caregiver's car on Otonga Rd in Rotorua at 3pm on Friday, running towards Old Taupo Rd.

He has a slim build and is about 180cm tall. He was wearing a green shirt with light-brown pants.

Speaking with the Rotorua Daily Post, Nigel's father Chris Peterson said his son was living in Rotorua under Geneva Healthcare's independent living programme where he was under 24 hour supervision.

Peterson said his son was struggling to cope with moving out of the house he had been living in for the past three years.

It was in the driveway of his new home that Nigel ran from the car.

His caregiver followed him for some time, but lost sight of him after returning to get help.

"[Nigel] thought he was losing his main security and there was no time in that instance to explain things to him before he bolted.

"For a regular person [moving houses] would have been nothing, but for Nigel his world came crashing down," Peterson said.

Geneva Healthcare chief executive Josephine Wallis said it was the first time an incident like this had occurred and that it couldn't have been predicted.

"This caught everyone by surprise. It's not like Nigel to do this and we hope he's safe and is found soon."

Wallis said they were undertaking a review to see if any changes could be made to prevent an incident like this from happening again.

Nigel's family said they received two unconfirmed sightings of him at the Arawa park racecourse at 2pm on Saturday, but he had not been spotted since.

His mother Eileen Goldsmith said he was raised on a farm and liked open spaces, which is why he may have gone to the racecourse.

They also urged the public to check their backyards and sheds, as he was most likely frightened and could be trying to hide.

"He doesn't interact with people he doesn't know and he can't tell the difference between a good or a bad person so he is extremely vulnerable," Goldsmith said.

The family feared Nigel's health had begun to deteriorate as he would not have been able to take his medication since he went missing.

They said he had an eftpos card which he knew how to use but they were not sure how much money was on the card or whether he was able to feed himself.

The family has checked with the owners of shops they think he may have gone to but have not heard of any more sightings.

They suspect there may be a chance he has tried to go back to Whakatane where he is originally from, but are not sure if someone would have given him a ride.

"If someone picked him up they would immediately know something isn't right," Goldsmith said.

Despite a large search party, Nigel's family are puzzled they haven't found him yet and are urging the public to help.

"We've been thinking that he is going to pop up at any moment but our concerns are mounting. People need to understand that he his lost, disoriented and frightened." Peterson said.

He said people should call 111 immediately if they spot Nigel and should keep him in their sight.

"He's not a threat to anyone, only himself," Peterson said.

If anyone has any information on Nigel Peterson's whereabouts, call 111 immediately or Rotorua police on (07) 349 9139 and quote file number 171117/2007.