Q: I am going to the prom this year and have decided to wear the same dress that I wore last year, for practical reasons (I am only a sophomore and the dress still fits me perfectly).

My dress is long, black and elegant, with spaghetti straps and a low, crisscross back
(down about 2/3 the length of my back). Here's my problem: Last year, I couldn't find a bra that would not show in the back (I am a 40 C cup and I need support). So, I had a strapless bra sewn into the dress until it reached the opening in the back. It worked fine until the day of prom; I put on the dress and the bra came unsewn!

I didn't have the time to sew it back in, so I went to the prom without a bra and was uncomfortable and self-conscious all night. Is there any style of bra that doesn't show straps AND has either a very low back or no back at all?

A: Assuming your dress has a really, really low back, what you want is a strapless, backless, longline bra -- one that goes down to the waist, or slightly below. Your best bet may be a local lingerie store or a big department store with a large bra department and helpful sales people. Some bridal shops also carry a selection of longline, strapless bras. You really have to try on the bra to know if it will be comfortable -- or, at least, bearable. Longline strapless bras don't have the greatest rep for comfort.

Meanwhile, you may have luck on the Web. Biggerbras has several strapless longline styles that come in your size for less than $40; Flattering.com also has some, but in the $60-$80 range.

The Carnival #313 at Brafitters looks promising, but the sizes range only up to 38C. The same is true for a couple of Wonderbra strapless longlines in the $28-30 range. These smaller bras might be worth trying since the circumference of your chest -- which your usual bra size is based on -- isn't as much of an issue with a backless longline.

Also, check out Clearbrastraps for transparent vinyl or silicone bra straps that hook onto a convertible bra.

Patricia McLaughlin is a nationally syndicated fashion columnist.
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