This paper descibes a pilot project in the Chemistry Library at Washington University in St. Louis using the Chemical Abstracts Document Delivery Service. In addition, results from a comparative analysis of nine commercial document delivery vendors are included. Vendors were compared according to cost, turnaround time, cost efficiency, fill rate, reliability and vendor responsiveness with responiveness with respect to delivery of individual documents. Recommendations are made with respect to vendor appropriateness in five science disciplines; Biology, Chemistry, Earth Sciences, Math and Engineering. The overall aim is to assist science librarians, wishing to implement such a service, in selecting document delivery vendors which would best meet their needs.