This is the final report of the evaluation of the DIALIB project--an investigation of the public library as a linking agent to major scientific, educational, social, and environmental data bases. The report is presented in seven sections and four appendices as follows: Section I provides an introduction to the study and a brief summary of the findings; Section II is a background section which describes the national background against which this study was connected; Section III is a discussion of the third year of the DIALIB project; Section IV compares the three years of the DIALIB project; Section V presents conclusions regarding online searching in the public library; Section VI describes problem areas which any library considering online searching must confront; Section VII discusses three areas in which additional research is needed; Appendix I contains statistical tables describing the DIALIB data; Appendix II is a study on the cost of online bibliographic searching in the DIALIB libraries; Appendix III is a "mini-study" of repeat users of DIALIB services; Appendix IV is another mini-study comparing local vs. network search systems in the DIALIB project. (Author)