YAHOO [BRIEFING.COM]: The S&P 500 suffered its worst single-session percentage loss in four weeks today, but it still made it out of October with its best monthly gain in nearly 20 years.

Market participants were inclined to sell today. They took their cues from overseas markets this morning and never really looked back. That left stocks to slog along with substantial losses and settle at session lows.

Last week Europe's leaders announced plans to shore up the continent's financial conditions, but it appeared that euphoria related to that announcement evaporated over the weekend. That prompted global participants to drop Germany's DAX and France's CAC for losses of more than 3%.

Confidence in the euro was also lost. In turn, it dove more than 2% against the greenback. The yen was an even poorer performing currency, though. It tumbled more than 3% after Japan's officials intervened in the currency in an effort to curb its strength after it had set a post-WWII record high last week.

Natural resource plays suffered the worst losses this session. That left the energy sector to tumble 4.4% and the materials sector to slide 4.2%. Financials weren't far behind; the sector fell 3.9%.

Defensive in nature, utilities made up the only sector that managed to find positive territory at all this session, but broad market weakness ultimately undermined its efforts and left it to log a 0.7% loss. It was the only sector to limit its loss to less than 1%.

Today's sell-off ate into the gains that the stock market had amassed in the course of the past four weeks, which had the stock market on track for one of its best monthly performances on record. Still, the S&P 500 finished October with a monthly gain of almost 11%, which is not only its first monthly gain since April, but it is also its best monthly performance since December 1991.

It was a relatively quiet start to the week for commodities. Strength in the dollar, stemming from a Japanese intervention on the yen, pressured prices. .. Precious metals traded sideways. Gold prices traded in a ~10 point range, while silver futures traded in a ~20 cent range. On the session, gold shed 1.2% to finish at $1725.20 per ounce, while silver ended lower by 2.7% at $34.36 per ounce. With today's losses, silver closed lower for the first time in seven sessions.

Crude oil ended lower by 0.1% at $93.32 per barrel. Futures managed to rally heading into the close to recoup most of their overnight losses. Natural gas finished higher by a penny at $3.94.

Advancing Sectors: (None)
Declining Sectors: Energy -4.4%, Materails -4.2%, Financials -3.9%, Industrials -2.5%, Health Care -1.9%, Tech -1.8%, Telecom -1.7%, Consumer Discretionary -1.5%, Consumer Staples -1.3%, Utilities -0.7%DJ30 -276.10 NASDAQ -52.74 NQ100 -1.7% R2K -2.6% SP400 -2.5% SP500 -31.78 NASDAQ Adv/Vol/Dec 560/1.77 bln/2007 NYSE Adv/Vol/Dec 556/1.11 bln/2464