From Friday: Market Share AMEX 2,983,423 ARCA 2,112,625 BATS 791,377 BOX 531,093 C2 279,797 CBOE 3,476,520 ISE 3,349,112 NSDQ 989,105 PHLX 3,857,437 OCC Totals 18,370,489 When you remove the S & P volume from CBOE, looks like ISE does the most "real" volume that you can participate on. AMEX is mostly directed order flow. PHLX is mostly crosses and directed flow. If you're a rebate trader, ARCA is king.