Theophylline intoxication is a common problem where prognosis of patients depends on the amount of ingestion, and the severity of manifestations, this makes further research on factors that, may affect the final outcome necessary.The purpose of this study was to assess the patterns of clinical presentations, demonstrate the predictors of severity and outcome of theophylline poisoning, and signify the clinical and investigative determinants of Intensive Care Unit (ICU) admission. A total of 100 patients with theophylline poisoning who were admitted to the Poison Control Center of Ain Shams University Hospitals were available for this study. The following parameters were the independent predictors of severity of theophylline toxicity; tachycardia, irritability, convulsions, theophylline level, hypokalemia, hypercalcemia, CK-MB level and cTn1level. In addition, hypokalemia and theophylline level were the predictors of severity between ages 15 and 45 years, and in females. Metabolic acidosis was the predictor above the age 45 years, and hypokalemia in males. Theophylline cut – off value of 47.5 μg/ml is indicator of toxicity, while a level of 82.5 μg/ml is an indicator of severe toxicity. Any case presenting to the poison control center with acute overdose of theophylline associated with convulsions, hyperthermia, hypokalemia, or serum theophylline level above 82.5 μg/ml should be admitted in the ICU.