This study developed and evaluated an instrument to measure the patient-nurse trust relationship in a medically underserved community. An exploratory sequential design was employed. In-depth interviews with 20 patients and 15 nurses were conducted to elicit their experiences regarding trust. Interview results were coded, analyzed and formatted into a Likert scale instrument. The instrument was administered to 120 patients. 19 items were retained for the final instrument with item-to-total correlational coefficients greater than 0.5, and a Cronbach's alpha of 0.95. Both construct validity and preliminary criterion validity were confirmed. Psychometric proportions of the instrument were established.