Researchers now say that a gun is present in one-quarter of all U.S. households, and being able to shoot the threatening intruder who enters your home is a favorite argument of those who support gun ownership. But, during a crisis, is a gun in the home more likely to kill you and yours or protect you?

Every once in a while, we read a newspaper story describing how a home robbery or assault was thwarted by a gun-wielding homeowner. More often, though, we read stories like the following:

News item from Baltimore, Maryland: A 15-year-old boy uses one of his father's guns to fatally shoot his father, mother, and two younger brothers. He has had a few minor arguments with his father over the years, but his schoolmates and teachers are shocked to hear that these shootings were allegedly carried out by an apparently stable and happy young man who was on the verge of becoming an Eagle Scout.

News item from Seattle, Washington: A 14-year-old boy died yesterday after he was accidentally shot in the head at the home of a friend.

Though I could find no information on how frequently a gun in the home is used to successfully protect the occupants, statistics abound that illustrate the dangers of guns kept in households. Here are some numbers from 2002 that illustrate the increased risks that come with keeping a gun in the house:

• Homicide of a family member is three times more likely
• Suicide of a family member, especially adolescents and young adults, is five times more likely
• During a family argument, an assault with a firearm is 12 times more likely to result in death than is an assault with, for example, a knife
• When the type of firearm was known to the statisticians, handguns were used in about 75 percent of gun homicides.

None of these statistics tells why I don't want a gun in our home. I'll never forget how the wife of a medical school classmate, who lived two floors above us, came close to shooting her husband when he returned late at night from his duties in the hospital emergency room. I can just picture myself being shot by someone — either friend or foe — in our darkened bedroom while I fumble around trying to locate and load some bullets into a gun.

And, conversely, if I were to keep a loaded gun in our bedside table, our young grandson might get hold of it.

One obvious, but frequently broken, rule for those who do have a gun in their homes: Keep the gun safely locked up in a place that children cannot possibly get into. (Of course, following this rule will make it harder for you to get at the gun when it is needed for protection.)

And one more precept for parents: When your child is going to visit a new friend for the first time, you should muster up the nerve to ask the new friend's parents, "Do you keep any guns in your home?"

A final downside of household guns: They are a favorite target of burglars and so their theft places yet more guns into the hands of criminals. People should promptly report to authorities if guns are stolen from their home.