There's a reason your mother bought you those panties with the days of the week embroidered on them when you were little. You need a fresh pair every day. And in a perfect world, you'd have just as many bras. But for most busy women, laundering bras every two or three wears is more realistic. Some underwear obsessives hand wash their delicates every few days, but, again, who has the time? Don't worry. Just put your bras and panties in a lingerie bag and toss the whole thing into the washing machine with the rest of your clothes. (Bed Bath and Beyond makes lingerie bags for $5 each, www.bedbathandbeyond.com.) Wash in cold water; if you'd like, use a gentle detergent like Woolite or Essence. Most panties are fine in the dryer, but extra-delicate items should be laid flat on a towel to air-dry.