Although lead pollution has long been known as a cause of poisoning, it has remained a challenge to reliably diagnose it due to its common symptoms in various diseases. In this article, we report two cases of acute loss of consciousness due to the ingestion of opium-contaminated with lead. The reported cases share patterns of symptoms similar to meningitis and encephalitis which are usual etiology for the loss of consciousness. Lead poisoning is not a usual etiology for loss of consciousness and is considered in cases of occupational or environmental exposure. These reported cases showed a pattern similar to meningitis and encephalitis, but due to the unusual manifestations during their admission and coexistence with gastrointestinal symptoms, we were led to consider poisoning as the cause of consciousness loss. Lead poisoning often goes unrecognized due to a low index of suspicion, but it may turn out to be fatal. Therefore, it should be considered in the differential diagnosis of any neurobehavioral deficits in substance abusers.