Hydrogen cyanamide is an active ingredient of Dormex® used as a plant growth regulator. Reports of the acute toxic effects of hydrogen cyanamide are limited. The emerging problem of Dormex toxicity approximately started in Egypt since 1997 and led to many deaths. Therefore, the aim of this study was to illustrate acute toxic effects of hydrogen cyanamide. Subjects and Method: The study was carried out on hydrogen cyanamide intoxicated cases presented to the poison control center (PCC), Ain Shams University Hospitals in the period between January 2006 and December 2009. Symptoms, signs, laboratory investigations, and complications were recorded at the time of presentation. The study was conducted on 12 patients with acute Dormex toxicity in addition to 10 healthy individuals serving as control. Conclusion: Dormex is highly toxic and may cause serious poisoning with acute toxic effects on central nervous system, respiratory and cardiovascular systems, liver, kidney, and hematological system. So awareness of this complications and early aggressive treatment are recommended to reduce mortality.