Noncompliance with neuroleptic treatment is a major barrier to delivery of effective treatment for schizophrenia outpatients. This article describes the development of a standardized measure for the assessment of attitudinal and behavioral factors influencing patient compliance with neuroleptic treatment. The Rating of Medication Influences (ROMI) scale was developed as part of a longitudinal study of neuroleptic noncompliance in schizophrenia and administered to 115 discharged schizophrenia outpatients. Analyses of the following were conducted to assess the scale's psychometric properties: (1) interrater reliability, (2) internal consistency, (3) principal components, (4) correlation with other subjective measures, and (5) correlation with independent family reports. Most (95%) of the ROMI patient-report items were reliable, whereas rater-judgment items were not reliable. The rater section was dropped. A principal components analysis of the reliable patient-report items yielded three subscales related to compliance (Prevention, Influence of Others, and Medication Affinity) and five subscales related to noncompliance (Denial/Dysphoria, Logistical Problems, Rejection of Label, Family Influence, and Negative Therapeutic Alliance). There were significant correlations between these subscales, and independently obtained family-report ROMI items were significant. The Denial/Dysphoria subscale correlated strongly with two other published measures of dysphoric response to neuroleptics, whereas the other noncompliance subscales did not. The ROMI is a reliable and valid instrument that can be used to assess the patient's subjective reasons for medication compliance and non-compliance. The subscale findings suggest that the ROMI provides a more comprehensive data base for patient-reported compliance attitudes than the other available subjective measures. Indications for use of the ROMI and other subjective measures of neuroleptic response are reviewed.