The purpose of this article is to test the applicability and utility of the Drug Evaluation Network Study (DENS), a timely electronic information system that tracks trends in substance abuse treatment. This article examines existing large-scale data collection efforts, discusses the rationale and design of the DENS system, and presents results of the DENS pilot phase. Clinical staff from more than 40 service delivery units in five cities were trained to conduct intake assessments on laptop computers with the computerized Addiction Severity Index (ASI). The DENS computer system also included an automatic data transfer protocol to allow regular transmission of ASIs and other data to a central server at Treatment Research Institute. Descriptive information and discharge status were also collected. Several problems were encountered during the early stages of the pilot phase, including obtaining consecutive cases from treatment programs, computerization and software application, treatment staff turnover, and assuring quality of data. Data is presented on 4,300 adults entering drug and/or alcohol treatment at the nonrandomly selected DENS pilot programs between June 1996, and April 6, 1998. Various examples of how DENS data can be used are presented.