This project tested the appropriateness of SERVQUAL (i.e., an instrument widely used in the service industry for assessing service quality based on repeated service encounters rather than a particular service encounter) to measure service quality in special libraries and developed a modified version for special libraries. SERVQUAL is based on an approach which views service quality as the gap between clients' perceptions of performance and expectations. This study was concerned with the match between the five underlying service dimensions in SERVQUAL (tangibles, reliability, responsiveness, assurance, and empathy) and values clients mention in connection with library services. Initial data-gathering consisted of interviews with focus groups in two special libraries. Results showed considerable commonality between the service qualities considered important by library clients and those in SERVQUAL but noted some specific library-related behavior that indicated these aspects. After incorporating the latter into SERVQUAL, feedback was obtained on the preliminary version of the modified instrument in a half-day interactive session with 15 librarians from a range of special libraries. The questionnaire was modified slightly, based on the librarians' input, then tested with clients in two special libraries. Tests indicated its validity and internal consistency across the dimensions but did not show the same five dimensions as the developers of SERVQUAL had discovered. The modified SERVQUAL, SLA (Special Libraries Association) version is appended. (Contains 64 references.) (Author/MES)