This study was conducted for the purpose of identifying discriminating, reliable, and valid criteria for evaluating substitute teacher performance which could be used by schools in developing an evaluation instrument;There is a great deal of apathy toward the plight of substitute teachers in our public schools today. It is extremely difficult to collect data on this population, especially obtaining a minimum of fifteen raters who are knowledgeable concerning the substitute teacher's performance. School employees often fail to adequately recognize and appreciate substitute teachers. In addition they often fail to even extend the barest minimum of professional courtesy to the people who serve our students well in this role, ignoring them to such a degree that when asked to assess their performance, some could not make such an assessment;Major findings of this study included: (1) Forty-nine of the fifty survey items discriminated or measured differences between the substitute teachers analyzed. (2) Rater observability of substitute teacher performance criteria did not vary greatly and generally the ratings were quite high. (3) Two or more of the evaluator groups had significantly different means for 21 of the 49 significant items. Student rated substitute performance on significant items lower than all other rater groups. (4) Item discrimination values utilizing gender as a discriminator could not be determined because of insufficient numbers of male raters for the analysis;It is recommended that substitute teachers have a separate evaluation instrument matching their unique needs, talents, and responsibilities in our public schools. A list of 40 performance criteria for substitute teachers based on discrimination power and observability are included for school use. (Abstract shortened with permission of author.)