The purpose of this study was to develop and validate an instrument to collect student judgments regarding their teacher's credibility. Items were developed and evidence of content validity generated. A pilot sample and a final sample of high school students were administered the Source Credibility Measure (SCM) so that actual response data could be used for instrument refinement. Both pilot and final data were submitted to factor analysis to explore construct validity. Reliability scores were also generated. Intertest construct validity evidence was generated for the final data. The study resulted in generating five factors represented by 29 items. These factors were Openness, Qualification, Communication Effectiveness, Defined Expectations, and Objectivity. The estimated alpha internal consistency reliabilities generated for these dimensions ranged from .77 to .89. The 29 item, five factor SCM Questionnaire is intended to be used as a feedback tool for inservice and preservice teacher training and individual teacher self-improvement. Further developmental work is needed to test the findings of this study. (Author/RC)