Alyce Payne has tried to quit before, but with little success.

"During my two pregnancies with my two children, I was able to stop," she said. "But the day they were born I started smoking again. The same day of delivery I smoked."

Tracy Bristow would hide in her garage to smoke so her two daughters couldn't see her.

"I have smoked their entire lives," she said. "I don't want to do that any longer. I want to be around for them."

Jose Castro believes his smoking is the reason his 19-year-old son took up the habit.

"He would always tell me not to smoke when he was little, and now he is going against what he was telling me," Jose said.

Meg Blakeman spent her childhood begging her parents and grandparents to quit.

"When I was little, I was the biggest nag," Meg said. "I once threw away my grandmother's cigarettes."

As a rebellious teenager, she picked up the habit. Now, nine years later, she is a nursing student and still smoking

Fighting Intense Cravings

Whether they have smoked nine years or 27, these four strangers all want to stop. But the cravings are intense.

"It comes and goes. And when it comes it's like, 'Ahhh, I want one now!'" said Jose.

"I walked out of the hospital," said Meg, "and I probably would have like cut off my pinky to have a cigarette. Oh, I just wanted one so bad."

Tracy's first day without a cigarette was full of frustration. She even snapped at her 9-year-old daughter, Emma, who is desperate for her mother to stay away from cigarettes. Her grandfather has emphysema, and her grandmother died from a smoking-related illness.

"I am worried that she'll end up like my grandpa on air [oxygen], and she'll die early like my grandma did," Emma said.

On Alyce's first day, she received a call from her quit-line counselor.

"I was doing really good," Alyce told her. "I was even scared to go out at lunch time because I knew I'd see people smoking. It's like you lost your best friend. It's so sad you can base your life on nicotine and feel that way."

Jose is surrounded by smokers, and his co-workers were skeptical that he could quit.

"I'm done," he told a colleague. "I'm not smoking anymore. So, if you see me smoking, I give you $100."

Today, on day four of their quitting process, they have resisted the urge to even buy cigarettes, but the weekend is coming and with it new pressures.

"This is really one of the biggest steps that I've chose to take in 27 years," said Alyce, "so I'm really nervous, but I really, really want to show everyone that I can do this."

ABC News' Bob Woodruff filed this report for "World News Tonight."