Stocks have been rallying relentlessly to post-crisis highs.

Meanwhile, the volatility index (aka the VIX, aka the "fear index") is near historic lows.

But according to UBS's Art Cashin, some options trader has made an enormous $11.25 million bet that the VIX will explode higher very soon.

And a rally in the VIX is usually accompanied by a drop in the stock markets.

From this morning's Cashin's Comments (emphasis ours):

A Very Big Bet In A Somewhat Unlikely Instrument – My friend, Jim Brown, the ever-alert consummate professional over at Option Investor pointed us to a rather unusual trade. Here's what he wrote in last night's edition of his valuable newsletter:

In past years I have reported on trades that were so large it appeared someone had inside knowledge of a pending event. Sometimes those were massive put positions on the S&P. A new trade just appeared that suggests there will be a market event in the near future. Last week somebody put on a call spread on the VIX using the April 20 and 25 puts. They bought 150,000 contracts for a net of $75 per contract. That is an $11,250,000 bet that the VIX will move over 20 over the next 60 days. You would have to be VERY confident in your outlook to risk $11 million on a directional position with the VIX at five year lows and the markets trying to break out to new highs.

Jim then goes on to list some of the scheduled events and deadlines visible over the next 60 days (mostly in Washington). When you add in the broad variety of geo-political possibilities, it's a decent reason to stay extra alert.

Hopefully, this person is wrong.

UPDATE: Art Cashin issued a correction in his February 8, 2012 Cashin's Comments. Here's what he said:

Optionland Errata – Several of our ever-alert readers pounced on an incongruity in our citation about that big volatility bet in the VIX options. As usual, they were correct. Jim Brown says there was a typo (damn computers). The spread should have read "call spread" (long the April 20 and short the April 25). At $75 per contract, the value of the bet was over $11 million. Mea culpa.

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