In the second half of the nineteenth century, the Ottoman government enacted various regulations to control the circulation and sale of poison in the Empire. Further, with the 1858 Penal Code, imprisonment and pecuniary punishment were introduced for the first time for vendors who sold poison without a guarantee from a third person. The aim of this effort to regulate poison sale was to prevent criminal poisonings along with other accidental poisonings caused by medical malpractices. However, as archival evidence reveals, there were certain obstacles that would hinder these efforts. Poison, especially arsenic and corrosive sublimate, had a vast range of applications and found many legitimate uses in daily life which is why poison continued to be available in demand in spite of the incessant precautions introduced in the field. Moreover, it seems that the laws and regulations enacted by the central government were far out of reach in the countryside. Throughout the period under research, poison murder and poisoning deaths because of malpractices by the pharmacists, unlicensed physicians, and lay healers received remarkable amount of attention by the government. This paper aims to explore the Ottoman government’s interventions to the business of poison sale by closely examining the legal records, especially the interrogation reports, based on a research in the Prime Ministry Ottoman Archives in ?stanbul. In an era of legal, economic, and administrative reforms, I argue, poison murder and accidental poisonings posed a serious challenge to the central government’s attempts for regulation and surveillance over its population. These cases, of course, do not only reveal the legal and institutional dimension of regulation on the poison issue, but also yield a complex narrative about the social and everyday life in the Ottoman Empire, such as the availability of poisons, patterns of marital conflict, the coping strategies with domestic violence, and attitudes toward women. By drawing on examples especially from the Rumelian and Anatolian countryside and utilizing particularly the interrogation reports of the murderers and the poison vendors, I will examine why poison murder started to pose a threat to the government’s efforts to diffuse its power in the countryside, while demonstrating, at the same time, the counter-effect of the local dynamics in this process. As an unaddressed question in the understudied social history of the Tanzimat period, this discussion may contribute to our understanding of the social life in the late Ottoman Empire.