Decoding your hospital bills: you can find and fix costly errors.

In April 2000, shortly after his father died, Richard Clarke went to Boca Raton, Fla., to check on his 84-year-old mother, Opal. She promptly handed him a shoebox stuffed with medical bills from 20 different providers who had treated his father. "She said, 'Here, you figure this out,'" says Clarke, 54. Despite the fact that he is a former hospital chief financial officer, Clarke says, "Even I couldn't tell what, if anything, she owed."

Sorting out the charges took him a year, but in the end he found about $2,000 in errors. "Dealing with it firsthand showed me how screwed up the billing system is," says Clarke.

Complaints about hospital bills are as ...