In a group of 93 pediatric patients with mediastinal masses, three quarters of them were diagnosed because they were symptomatic. Approximately one half of the masses were malignant, and of neurogenic or lymphomatous origin. Neurogenic tumors predominated before the age of 4 years, while lymphomas were most common beyond age 4. Two thirds of the malignancies were potentially curable by surgery, irradiation, and chemotherapy; 54% of the patients were salvaged. Enteric duplications, ganglioneuromas, bronchogenic cysts, hemangiolymphangiomas, thymic cyst, and teratomas were the most frequently occurring benign masses. Simple excision was uniformly effective in these lesions.