An investment/trading strategy that exploits divergences between actual and theoretical futures prices. An example is the simultaneous buying (selling) of stock index futures (i.e., S&P 500) while selling (buying) the underlying stocks of that index, capturing as profit the temporarily inflated basis between these two baskets. Often, the point at which profitability exists is expressed at the block call as the number of points the future must be over or under the underlying basket for an arbitrage opportunity to exist. See: Program trading.