This chapter examines strengths and weaknesses of archival research, with an emphasis on some of the poorly appreciated strengths. The chapter focuses on two heuristics that can guide the design of sound archival research. The first heuristic (“OOPS”—i.e., operationalizations, occasions, populations, and situations) is a checklist for critically analyzing and maximizing external validity. The second heuristic (“GAGES”—i.e., geography, age, gender, ethnicity, and SES) draws attention to five of the most worrisome confounds that threaten internal validity. After introducing these heuristics, I review some illustrative examples of sound archival research that has offered new insights into topics as diverse as social judgment, the self-concept, and longevity. By providing such examples, I hope to inspire others to pursue rigorous and creative new programs of archival research.