I believe ISE uses proprietary put/call info generated on their exchange add a fudge factor and publish meaningful data asit applies to the overall indexes (QQQ, IWM, SPY, DIA). I recently attended a conference where the ISE option exchange gave a pitch for their product(s) and showed how to use them. They also said traditional put/call ratios without the commercials removed and the fudge factor implemented were NOT useful. They also talked a little about individual issues and yes that data can be used as well.