Background: Hyperthyroid patients are commonly given antithyroid drugs as treatment or as preparation for a more definitive therapy such as radioactive iodine or surgery. Among the side effects of antithyroid drugs, the rare occurrence of agranulocytosis (less than 1 percent) is the most feared for this has a mortality rate as high as 21.5 percent. Objective: To compare the severity of agranulocytosis among patients on antithyroid drugs; to describe the clinical profile of patients with agranulocytosis; and to compare the clinical factors based on the levels of absolute neutrophil counts (ANC). Methodology: Retrospective, descriptive analysis of records of patients with antithyroid drug-induced agranulocytosis (ANC 37 ANC 192 vs 679, p=0.41). Slightly higher ANC was seen among well nourished individuals than those who were underweight (ANC 569 vs 194, p=0.54). Patients on propylthiouracil had severe agranulocytosis than those taking imidazole compounds (ANC=174 vs 31, p=0.38). PTCI above 300 mg/day was significantly correlated to lower levels of ANC (ANC=71 vs 380, p=0.023). Statistically low ANC counts were seen among those who died (ANC=24 vs 504, p=0.011). The use of G-CSF improved the outcome of patients with agranulocytosis (p-value .035). Conclusion: PTG >300mg/d was correlated to agranulocytosis. Mean ANC of 24 was correlated to poor outcome. The use of G-CSF improved the outcome of agranulocytosis.