Studies in many societies have shown low to moderate agreement between reports of psychopathology by different informants, including self-reports by the people being assessed. Research has also shown that psychiatric diagnoses based only on self-reports are often wrong when compared with diagnoses based on multiple sources of data. Furthermore, reports from different informants predict different aspects of outcomes. Because different informants can contribute valuable information about an assessed person’s functioning, comprehensive clinical assessment should include data from multiple informants. Practical methods were presented for obtaining, comparing, and using data from multiple informants scored in relation to norms for the age and gender of the assessed person, the type of informant, and appropriate multicultural norms. When deemed appropriate, clinicians can show clients bar graph comparisons of scale scores from multiple informants to foster therapeutic alliances and to evaluate progress and outcomes. Although more research on multi-informant data is warranted, applications of existing knowledge and instruments can advance clinical services now.