Dumb question but I'm confused: The underlying price of say a July VIX Option is the JULY VIX future or is it the AUG VIX future? The CBOE site says the following: For example, VIX options expiring in May 2006 will be based on SPX options expiring 30 days later - i.e.; June 2006 SPX series. In fact, June SPX options do not even enter into the spot VIX calculation until April 17, 2006. Thanks!