This article explores the approach of dementia paralytica by psychiatrists in the Netherlands between 1870 and 1920 against the background of international developments. The psychiatric interpretation of this mental and neurological disorder varied depending on the institutional and social context in which it was examined, treated, and discussed by physicians. Psychiatric diagnoses and understandings of this disease had in part a social–cultural basis and can be best explained against the backdrop of the establishment of psychiatry as a medical specialty and the specific efforts of Dutch psychiatrists to expand their professional domain. After addressing dementia paralytica as a disease and why it drew so much attention in the late nineteenth and early twentieth century, this essay discusses how psychiatrists understood dementia paralytica in asylum practice in terms of diagnosis, care, and treatment. Next we consider their pathological–anatomical study of the physical causes of the disease and the public debate on its prevalence and causes.