Ten cases of ingestion of yellow phosphorus rat poison, including four cases that occurred during the past 3 years, are reported. Comparison of these cases with 82 others from the literature showed that ingestion of yellow phosphorus paste often results in clinical findings that are different from those described for acute yellow phosphorus poisoning in current toxicology texts. The time lag between swallowing of the poison and onset of symptoms varied from a few minutes to 24 h. Garlic odor, mucosal burns, and phosphorescent vomitus or feces occurred in only a small percentage of cases. Diarrhea was not a presenting complaint. Initial symptoms were referable to the gastrointestinal tract, central nervous system, or both. Mortality rates were 23% for patients who had early symptoms of vomiting or abdominal pain; 73% for those where the first manifestation of intoxication was restlessness, irritability, drowsiness, stupor, or coma; and 47% for patients who had a combination of these GI and CNS symptoms initially. Applying standard diagnostic criteria for yellow phosphorus poisoning to patients who have consumed yellow phosphorus pastes may result in serious diagnostic errors.