Statistically based ranked retrieval of records using keywords provides many advantages over traditional Boolean retrieval methods, especially for end users. This approach to retrieval, however, has not seen wide-spread use in large operational retrieval systems. To show the feasibility of this retrieval methodology, re-search was done to produce very fast search tech-niques using these ranking algorithms, and then to test the results against large databases with many end users. The results show not only response times on the order of 1 and l/2 seconds for 806 megabytes of text, but also very favorable user reaction. Novice users were able to consistently obtain good search results after 5 minutes of training. Additional work was done to de-vise new indexing techniques to create inverted files for large databases using a minicomputer. These techniques use no sorting, require a working space of only about 20 % of the size of the input text, and produce indices that are about 14 % of the input text size.