BACKGROUND Nonfunctioning pituitary adenomas are the most common pituitary adenomas in adults and cause significant morbidity unless adequately treated. METHODS This study retrospectively assessed the medical records of 160 patients operated via pure endonasal endoscopy. The presenting symptoms, results of neurologic and visual examinations, levels of pituitary hormones, results of radiologic examinations, size of the adenoma, rates of resection, results of postoperative visual examination, and pituitary hormone levels at follow-up were recorded to establish the appropriate approach, operative criteria, and outcomes of patients with nonfunctioning pituitary adenoma. RESULTS Headache was the presenting symptom in 87.5% of the patients. Thirty-three percent had visual loss, and visual examinations on the whole study population revealed a visual field defect in 47.5% of the patients. Only 16.25% of the patients presented with endocrinological symptoms; 52.5% had abnormal anterior pituitary hormone levels. Regarding adenoma size, 56 patients had macroadenoma (35%), 84 (52.5%) had mesoadenoma, and 20 patients had giant adenoma. Gross total resection was achieved in 90% of the patients; subtotal resection was achieved in the remainder. The rate of total resection was lower for giant adenomas and recurrences. Visual symptoms and anterior pituitary hormone levels improved in 27 and 42 patients, respectively, after the operation. CONCLUSIONS Nonfunctioning pituitary adenomas present frequently as mesoademonas and giant adenomas. Patients with these tumors may have subclinical visual or hormonal deficits at the time of diagnosis. Early and effective surgical treatment is essential for rapid recovery of visual and/or hormonal deficits, particularly in symptomatic cases.