The purpose of this study was to develop a valid and reliable assessment measure for stringed instrument performance. In the initial phase of the investigation, a total of 90 suitable statements were generated for the initial item pool gathered from essays, statements, and previously constructed rating scales. These statements were put into the a priori categories determined by previous research. These items were paired with Likert-type scales and used by 50 judges to assess 100 recorded string performances at the middle school through high school level. The results of the initial item pool were factor-analyzed using a varimax rotation. Five factors were identified (interpretation/musical effect, articulation/tone, intonation, rhythm/tempo, and vibrato), and 28 items were selected for the subscales of the String Performance Rating Scale (SPRS) based on factor loadings. Reliability varied from .873 to .936 for each judging panel using Hoyt's analysis of variance procedure. Two studies were conducted to establish criterion related validity, with zero-order correlations ranging from .605 to .766 between the SPRS and two other rating scales.