OBJECTIVE This study investigated firstly the change of intraocular pressure (IOP) after injection of intravitreal triamcinolone acetonide (IVTA) for the treatment of macular edema and secondly the factors that influence these changes. METHODS A prospective, non-comparative study was performed in 60 patients at Kangnam Sacred Heart Hospital from October 2003 to September 2004. All the patients received 4-mg IVTA injection. RESULTS Mean IOP was elevated from the day after injection and peaked at 20.5 mmHg after 2 months (p=0.000). Twenty-six eyes (43.3%) showed significant IOP elevation. IOP was not controlled despite full glaucoma medication in 7 (11.7%) eyes. Two eyes underwent filtering surgery. Younger age was a statistically significant predictive factor for IOP elevation (p=0.009). CONCLUSIONS In this study, patients who needed filtering surgery developed an IOP spike within one week after the injection. Therefore, clinicians should consider checking IOP at the end of the first week. Furthermore, greater cautions is mandatory with relatively younger patients.