Although the typical study in psychology involves the quantitative analysis of contemporary research participants, occasionally psychologists will study historical persons or events. Moreover, these historical data may be analyzed using either qualitative or quantitative techniques. After giving examples from the subdisciplines of cognitive, developmental, differential, abnormal, and social psychology, the distinctive methodological features of this approach are outlined. These include both data collection (sampling, unit definition, etc.) and data analysis (both qualitative and quantitative). The discussion then turns to the advantages and disadvantages of this research method. The article closes by presenting the reasons why (a) psychologists will probably continue to use historical data and (b) quantitative analyses may eventually replace qualitative analyses in such applications.