A description is provided of the Experimental Time-Sharing System (ETSS), a multi-language, general-purpose time-sharing system designed to support a wide range of computing applications. Included among these are the control of an on-line behavioral research laboratory. Major topics discussed in the report are: 1) the system's hardward configuration; 2) the operating system software; 3) interfacing and the control of laboratory devices; 4) the ETSS input/output command structure; 5) the initiation and timing of multiple input/output processes; 6) task scheduling and memory management; and 7) overall system performance and cost. (PB)