It's been 30 years since "Dallas" first hit the airwaves, but Larry Hagman, who played J.R. Ewing -- the fictitious Texas oilman that viewers loved to hate -- is still going strong.

"My health is, I hope, pretty good," Hagman tells ET's Thea Andrews. "I just had my blood tested yesterday. I do it every two months or so. I had a liver transplant 14 years ago, so I have to keep on top of that, but I've got 14 years of it."

As a result, the veteran actor works with the National Kidney Foundation, encouraging people to become donors.

"Eighteen people die every day waiting for an organ," Hagman explains. "And that's ridiculous. There's a cure for all these diseases if people just give up their organs and don't take them with them when they pass on."

Hagman, who also works with the American Cancer Society -- he had a brief battle with cancer shortly after "Dallas" wrapped -- and is a proponent for solar power, having solarized his entire home, is actually chatting up the ninth season DVD release of "Dallas."

It was a landmark year for the series, because it was the year that Bobby (Patrick Duffy), J.R.'s brother, returned from the dead. What was so unusual about it was that in order for Bobby to come back, the writers had to come up with an explanation for all the events of the previous season, which featured his funeral and life after. They came up with the idea of having the previous season be a dream sequence -- which threw viewers into a tizzy and is a storyline plot that is still talked about today.

"I knew Patrick was coming back," Hagman shares. "I didn't know how they were going to do it. They filmed him when Irish Spring or something like that did a commercial. They shot the whole day just for one thing, he opens the door and says, 'Good morning.'"

The cast of "Dallas" was a close one and its stars – Hagman, Duffy, and Linda Gray (Sue Ellen, J.R.'s wife) remain so today.

"Patrick and I are good friends. We go hunting and fishing a lot. Linda Gray and my wife and I have lunches or dinner a couple of times a month," Hagman shares.

"Dallas -- The Complete Ninth Season" is now in stores.