At lunch the other day, my sister made the kind of announcement that begins with sitting up very straight and folding your hands on the restaurant table.

At lunch the other day, my sister made the kind of announcement that begins with sitting up very straight and folding your hands on the restaurant table.

"I quit smoking 31 years ago today," she said.

She quit, she told our lunch companions, for the sake of her then-10-week-old niece. The birth of that child - my daughter - had made my sister feel both mortal and at a dangerous disadvantage.

She wanted to see her niece grow up, my sister said, so she quit smoking to maximize her chances.

As for me, I wanted to see my daughter grow up too, but I couldn't quit smoking because I'd never started. Instead, I aimed for improved nutritional health by baking all our bread, rolls, sandwich buns and pizza. I made pancakes without Bisquick; I boiled my own bagels and knotted my own pretzels and shaped my own pita pockets. Listen, I even rolled my own crackers. You can't get crazier than that.

My point, though, is that my sister really did quit smoking. For good. Forever. Finished. Never again.

It was the hardest thing she'd ever done, she has said, even with a good program to follow, strong people to offer support and a bundle of motivation in a terrycloth sleeper.

I hear her talk about the awful craving that accompanies not smoking, the organic longing, even years later, when the former smoker knows she won't start up again, has no real desire for a cigarette anyway, and yet, and yet I hear all that and feel a relief that almost leaves me weak in the knees that I never started.

And why didn't I? We both grew up in the same household, raised by the same single mother, a smoker who'd started when smoking was a misunderstood habit, almost considered a health cure, and who now couldn't stop, although she'd tried.

As children, my sister and I both despised cigarettes. We both urged our mother to quit and sighed with frustration when she didn't; and when the surgeon general's report came out in 1964, we both fairly trembled with alarm. Then my sister went off to college, and within weeks she was smoking too. First in bars, so she could join the girls she admired who played some game involving cigarettes and napkins, and later in the wider world.

In those days, of course, it seemed like everyone smoked. Restaurants were full of smokers; smoking was permitted on buses and airplanes and in business offices and teachers' lounges. As part of my college requirements, I completed an internship at a house for teenage runaways. Staff meetings were held in a narrow windowless basement room, where more than a dozen people smooshed together on couches as if attending a slumber party in a closet, everyone smoking but me.

I was never tempted to start. I loved my mother and although I was shallow for my age I knew even then that it took real pluck for a shy single woman to raise two daughters in a world that still considered divorce the social equivalent of eating your young.

But I abhorred her smoking. I hated the smell in the car and on clothes; I hated emptying ashtrays; I hated even more having to clean cigarette butts off my mother's dinner plate.

I didn't want to touch cigarettes, smoked or unsmoked. Flakes of tobacco affect me the way thick furry spiders affected other people. Although I had friends who smoked, I never changed my mind or even softened my position about the habit itself. I'm a fanatic, really. I don't deny it.

Anyway. My sister quit for love of my daughter, and she did get to see that baby grow up.

"It was 31 years ago today," she repeated.

We all were silent for a few moments while I, at least, contemplated the most mind-reeling aspect of her story: that I have - holy moly! - a 31-year-old daughter.

In a larger, more scientific sense, though, my sister and I would have made a fine study for a psychological journal, or maybe for a tabloid newspaper: "Raised together: one smoker, one Looneytune," the headline might have read.

And the punch line to that thought?

You can quit smoking.

Margo Bartlett is a ThisWeek staff writer: E-mail mbartlett@this