<span name="style_bold">Objective:</span> To develop a valid and reliable instrument to assess the perceived quality by the users of pharmaceutical services in the Costa Rican Public Health System. <span name="style_bold"> </span> <span name="style_bold">Methods:</span> It was developed an instrument conformed of three dimensions: technical, interpersonal, and environmental, with 53 Likert scale items. It was evaluated by four pharmacy professionals with extensive experience in investigative, administrative and clinical areas, from which turned out in a questionnaire of 49 questions applied to 115 users of the Pharmacy from the San Rafael de Alajuela Hospital. To analyze unidimensionality was applied factor analysis, for reliability the item-total correlation, and for internal consistency Cronbach’s alpha. The statistical package used was SPSS, version 17. <span name="style_bold"> </span> <span name="style_bold">Results: </span>Factor analysis determined unidimensionality in the instrument, the first factor accumulated 30,1% of the total variance and the second 8,1%, which means that all the items that comprise the actual indicator is measuring a single construct theoretical, that means that forms a scale. Reliability analysis suggested the elimination of five items and another by aspects of internal consistency, for a final Cronbach’s alpha of 0,951. <span name="style_bold"> </span> <span name="style_bold">Conclusions:</span> This is the first valid and reliable instrument for measuring perceived quality in pharmacy units of Costa Rican’s Social Security This is the first valid and reliable instrument for measuring perceived quality in pharmacy units of Costa Rican’s Social Security

perception; pharmaceutical services; health care; Costa Rica