The investment seeks to track the results of a fully collateralized investment in futures contracts on the S&P GSCI? Total Return Index. The Trust holds long positions in index futures that have settlement values at expiration based on the level of the S&P GSCI-ER at that time, and earning interest on its non-cash Collateral Assets used to satisfy applicable margin requirements on those index futures positions. The index reflects the return of the S&P GSCI-ER, together with the return on specified U.S. Treasury securities that are deemed to have been held to collateralize a hypothetical long position in the futures contracts comprising the S&P GSCI?.