No matter what time of day or night the phone rings, the voice that summons me sounds tired and desperate. But that's not the only reason I go. I'm known there, so I seldom wait long before someone comes for me, leads me into the little room, closes the door, asks to see my ID card.

This time it's a young black woman who taps a few keys, looks at the computer screen and says, "You've done this before."

"A few times," I reply. She props my the card on the desktop, enters some codes, glances at my bare arms, strikes a key or two.

If I am nervous, she may become suspicious and uneasy, so I fold my hands loosely in my lap, place my feet flat.

She clears her throat, begins reading the first question. My scars prove I've done this dozens of times, but my mouth is dry and my voice squeaky.

She glances at the computer monitor, perhaps checking to see if my answer matches the one I gave the last time I was in this claustrophobic office. The screen is tilted away from me, so I can't tell what additional information she may have. My only chance is to tell the truth as I remember it and hope that the answers I gave last time were recorded correctly. Her questions grow more complicated every time she opens her mouth. I choose to reveal these intimate details of my past. I can leave anytime; the door is not locked. She has no power to hold me here.

She asks another question. Have I ever....?

I tell myself this facility promises confidentiality, and in 25 years I have had no reason to doubt it. No, I tell her. I haven't.

The truth is important here. In our world, some people are casual about the distinction between truth and falsehood; others get rich from telling lies. But in this room, the difference between truth and a lie may be, in the old cliche, a matter of life and death. Not mine, but someone who will never know me if I am truthful.

Do I know anyone, she asks, who has. . . .

No, I say. Faces of my friends flash before my eyes. I resist the urge to cross my fingers. I've known people who might not have been able to answer that question honestly and remain in this room. But years have passed; I've lost track of them.

Have I been, she asks, in any of the following countries since 1977: Cameroon, Central African Republic, Chad, Congo: the list goes on, countries of which I know nothing. Her voice has no particular inflection; she's probably never been to any of those places either.

She takes a deep breath. Have I traded sex for money or drugs since 1977?

I think about 1977. She probably wasn't born yet. Sometime that year I remember reading an article insisting that I was more likely to be raped and murdered than to marry again. I was poor, but I did have a job, an old car, an apartment. I wasn't tempted to trade sex for money or drugs. In fact, most of my experiences with drugs had occurred a decade earlier, in the 1960s. Money wasn't involved, since none of us had any. I decide that attempting to joke about these memories with this serious young woman would not be prudent.

Soon she drops her pen, clicks a few keys on the computer, and leads me to a couch under a glass ceiling.

I show the technician my arms, and she swabs the left one with iodine, suggesting I look away. But I watch as she slips the needle deftly into a fat blue vein. The spot feels briefly as though a match had touched it, and then a richly red stream begins to flow through the tube and into the bag rocking beside me.

Lying back, I watch birds fly across the windows and think of healing for whoever receives this transfusion. I love cows, eat meat, carry a pistol, and have strong and specific political viewpoints. My blood may pour into the veins of someone who opposes everything I believe in.

That's exactly the reason to do this. Blood donors can't impose their will on the people whose lives they may save. When I'm depressed about anything in my world — and these days that feeling sweeps over me fairly often — I find relief with United Blood Services. Here, the only thing that matters is giving freely that another shall receive.

Linda M. Hasselstrom is a contributor to Writers on the Range, a service of High Country News in Paonia, Colorado (hcn.org). She writes in Cheyenne, Wyoming.