Conclusions regarding the significance and appearance of the adenoids incidentally noted on magnetic resonance (MR) scans of the brain largely rely on observations of previously published plain film data. In order to determine the age specific appearance of normal adenoid tissue as measured on sagittal T1-weighted midline MR images, we evaluated 189 patients without a history or clinical evidence of adenoid disease, who were sequentially referred for an MR scan of the brain. The thickness of the adenoid pad was measured to the nearest 1 mm along a line through the pharyngeal tubercle constructed perpendicular to the anterior clival surface. Patients were grouped according to age. Normal subjects demonstrated an age specific variation in the size of the pad with the maximal size being attained in early childhood and then steadily decreasing in later childhood and adulthood (P = 0.0001). The adenoids were largest in the 7-10 years age group (mean, 14.59 mm) and steadily declined to 4.83 mm by 60 years of age. Previous surgery had no effect on adenoid measurement (P = 0.582). Magnetic resonance scans provide an excellent method for assessing the adenoid pad.