The application of magnetic resonance imaging (MRI) scanning in the diagnosis of acoustic neuroma (AN) has increased the relative incidence of smaller tumors and has impacted on the typical clinical presentation of AN patients. The charts of 126 patients treated at the University of California, San Francisco for newly diagnosed AN from 1986 to 1990 were reviewed. Twenty-four percent of tumors fell into the smallest size category (< 1 cm); this was a substantial improvement over earlier series. However, 16% of tumors remained undiagnosed until they achieved large size (> 3 cm). The incidence of hearing loss, dysequilibrium, headache, facial numbness, and diplopia all increased with increasing tumor size, while the incidence of vertigo decreased. Diagnosticians should not overemphasize "typical" symptom complexes, as substantial variability in clinical manifestations exists. An improved awareness by clinicians of the variability of AN presentation will improve diagnostic efficiency and continue the trend toward earlier diagnosis of these lesions.