The purpose of this study was to evaluate the safety and efficacy of echocardiographically (echo) guided pericardiocentesis in pediatric patients. Echo-guided pericardiocenteses performed in pediatric patients (age ≤16 years) at the Mayo Clinic between 1980 and 1997 were identified. Presentation, cause and characteristics of the effusion, details of the pericardiocentesis procedure, and outcome were determined by comprehensive chart review supplemented by telephone interviews when necessary. Seventy-three pediatric patients, median age 6.7 years (range 1 day to 16 years), underwent 94 consecutive echo-guided pericardiocenteses for effusions of various causes. Twenty-one (22%) procedures were performed in children younger than 2 years. All but 1 procedure were successful (99%). A mean fluid volume of 237 mL (range 4 to 970 mL) was withdrawn. Only a single attempt was needed for entry into the pericardial space in 87 (93%) procedures. No deaths were associated with the pericardiocentesis procedure. Only 1 major complication occurred (1%), a pneumothorax requiring chest tube reexpansion. Three (3%) minor complications—2 instances of right ventricular puncture and a small pneumothorax—did not require treatment. Extended catheter drainage for a mean of 5.2 ± 4.5 days (range 1 to 19 days) was used with 30 (32%) of the 94 procedures. For the 52 patients who underwent pericardiocentesis without catheter drainage as the initial management strategy, 18 required 21 repeat pericardiocenteses for recurrence of effusion. In contrast, for the 21 patients who had pericardial catheterization as the initial management strategy, none had recurrences necessitating a repeat procedure (P < .001). Increased utilization of a pericardial catheter was associated with a concomitant decrease in the number of surgical pericardial procedures over the study period. Echo-guided pericardiocentesis was the only therapeutic modality for the management of effusion in 73% of all patients. Echo-guided pericardiocentesis is safe and effective in pediatric patients, including children younger than 2 years. The increasing use of pericardial catheterization in conjunction with this technique was associated with significant reduction of recurrence and decreased frequency of surgical interventions for treatment of pericardial effusion. Echo-guided pericardiocentesis with extended catheter drainage should be considered as primary management strategy for clinically significant pericardial effusions in pediatric patients. (J Am Soc Echocardiogr 1998;11:1072-7.)