OBJECTIVES: To develop and validate a scale to measure patients' trust in pharmacists for use in future pharmacoeconomic studies METHODS: After literature review to provide reference for scale development, focus group discussion was then carried out to assess the relevance of constructs generated and further explore any new potential domains or items. A candidate version based on 7-point Likert scale was developed and pilot-tested for content validity, after which the finalized version was tested among eligible Singaporeans across different ethnic and age groups. Score distributions were assessed for discriminatory power. Item analyses were done to ensure the corrected item-total correlation coefficients should be greater than 0.30 for finalized items. Exploratory factor analysis was used to determine dimensionality and suitable homogeneous items. Reliability was measured by Cronbach's alpha to evaluate internal consistency. Pearson's correlation coefficients were studied for construct validity. RESULTS: Altogether 18 items were generated with good variability (SD>1.0) and symmetry (means ranged from -1 to 1) for score distribution. After minor changes to improve content clarity, finalized questionnaire was self-administered among 1196 eligible respondents [mean (SD) age: 38.6 (14.9) years, 51.6% female, 87% >6 years of education]. Six items were dropped due to inadequate item-total correlation coefficients, leaving 12-item scale for factor analysis. Three factors (“benevolence”, “technical competence” and “global trust” of 6, 4 and 4 items respectively) were then identified accounting for 55% of the total variance. Cronbach's alpha was 0.83, indicating high internal consistency. As hypothesized, construct validity was demonstrated by the statistically significant correlations between trust with patient's satisfaction with pharmacist's service (r=0.54), returning for care (r=0.30) and preference of medical decision-making pattern (r=0.16). CONCLUSIONS: The 12-item trust in pharmacists scale demonstrated high reliability and construct validity. Further studies among other populations are suggested to confirm the robustness and even improve the current scale.