The sexological research questionnaire, which became a central research tool in twentieth-century sexology, has a methodological-developmental history stretching back into mid-nineteenth century Germany. It was the product of a prolonged, disruptive encounter between sexual scientists constructing sexual case studies along with newly assertive homosexual men supplying self-penned sexual autobiographies. Homosexual autobiographies were intensely interesting to these men of science but lacked the brevity, structure, and discipline of a formal clinical case study. In the closing decades of the century, efforts to harness and regularize this self-penned material resulted in a series of methodological adaptations. By the turn of the century this process had resulted in the first use of a formal sexual research questionnaire.