Abstract: A data retrieval system in which data to be retrieved is stored in the memory of a host computer and accessed from user terminals which transmit requests for data to the host. Data is stored in the host computer in the form of a series of search terms arranged in a predetermined logical order, and each stored search term is stored with associated data to which users require access. Data retrieval requests are entered by users in the form of search terms corresponding in logical structure to the search terms stored in the host computer. The host computer memory is partitioned into a series of blocks in each of which is stored both search terms falling within a respective predetermined range of the logical order and the data associated with these search terms. Each user terminal has a memory in which is stored an index that cross references the memory address of each block in the host memory with the range of search terms stored within that block.