A transistor-driven magnetic-core memory which has a capacity of 1024 18-bit words has been built and is being studied. Both the read and write operations employ the coincident-current technique. The memory-drive currents are developed by transistors and the desired memory location is selected by magnetic-core selection switches. Eighteen thousand, four hundred and thirty-two memory cores are used in the storage array, 48 switching cores are used in the selection switches, and 160 transistors are used in core-driving circuits and read-out amplifiers. A typical memory cycle, reading followed immediately by writing, requires 20 microseconds.