Reliable and valid tests / instruments are the foundation of good research. They need to be developed carefully following acceptable scholarly procedures. The procedure for developing a test / instrument is a long and complicated one. This paper describes in detail the process of developing an instrument for the identification and validation of competencies required for medical librarians. The understanding of the process of designing an instrument is important as it helps in assessing its validity and reliability. Therefore, this paper describes in detail the various steps that were undertaken to develop the instrument.