In this series, we take a look at the 25 stocks on the S&P 500 Index (SPX) that have turned in the worst performance during the past decade -- what went wrong, and what happens next.

Former hippies might notice that the ticker symbol for Tenet Healthcare Corporation (NYSE: THC) is also the acronym for the active compound in marijuana, but this apparent inattention to detail is likely the least of the company's concerns. When Tenet was formed in 1995, it was born out of a merger between American Medical International and scandal-plagued National Medical Enterprises. Executives at the newly reborn healthcare services company hoped that its new name would help erase any unpleasant investor associations with its previous incarnation.

What went wrong? At number 19 on our list of SPX losers, THC shed 73% of its value during the 10-year period ending June 30, 2008. Prior to a stomach-churning sell-off in the fall of 2002, the shares were entrenched in a near-vertical uptrend that peaked at $52.50. It seems that a seedy healthcare services company by any other name ...

October 2002 marked the stock's peak, as well as the beginning of its steep descent. First, the company reported fiscal first-quarter earnings that surpassed analysts' estimates by 2 cents per share. A few weeks later, Tenet was named co-defendant in a lawsuit filed by the widow of a man who'd accepted an artificial heart, which she alleged "stripped him of his human dignity." This relatively minor suit, worth just $100,000, wouldn't break THC -- but it nonetheless heralded the beginning of the end. Toward the end of the month, the shares tumbled sharply after an analyst downgraded Tenet and warned that it was too dependent on Medicare reimbursements from the government.