Chemical Abstracts Service developed and expanded a computer-based Chemical Registry System and operated it on a large-scale pilot basis. Some 1,744,319 registry transactions were made, resulting in the addition of 988,806 unique substances to the Registry Files. Continual effort has been made to improve computer capabilities and procedures, add new types of compounds, and improve user services and programs. In addition to registration, this included (1) the testing of alternative input methods for chemical information, including the development of special keyboards and keyboarding conventions; (2) the installation of several operational adjustments in the System; and (3) the development of computer support systems. Tabular data are included to show various operations and characteristics of the System. (RR)