An apparatus and method for penetrating bone marrow is provided. The apparatusmay include a housing such asa handheld body, a penetrator assembly, aconnector that releasably attaches the penetrator assembly to a drill shaft, agear mechanism, a motor and a power supply and associated circuitry operableto power the motor. The penetrator assembly may include a removable innertrocar and an outer penetrator or needle. It may also include agrooved trocarthat allows bone chips to be expelled as the apparatus is inserted into bonemarrow. Various connectors are provided to attach the penetrator assembly tothe drill shaft.
