This paper describes a study that attempted to ascertain the degree of success that undergraduates and graduate students, with varying levels of experience using the World Wide Web and Web search engines, and without librarian instruction or intervention, had in locating relevant material on specific topics furnished by the investigators. Because different search engines use dissimilar search protocols and interfaces, potential problems paralleling those perceived in CD-ROM and online searching were of concern. Results of the study demonstrate that most end-users can effectively use at least two search engines without professional assistance. The reasons for the contrast in end-users' success with World Wide Web search engines compared with problems found in other types of database searching appear to be related to the effectiveness of WWW search engines' software, which can quickly scan a large number of documents and weight the retrieval for relevance. While online database and CD-ROM vendors have made proprietary search syntaxes standard, Web search engines generally provide for natural language searching. The success of users' searches is no longer necessarily contingent on a knowledge of search protocols but rather on the ability to identify correctly the key concepts for which they are searching. (Contains 30 references). (Author/SWC)