We retrospectively reviewed the number and types of diagnostic electron microscopic specimens from a 4 1/2-year period. During this period, the number of fine-needle aspirate biopsy specimens processed increased in a linear fashion, from a relatively uncommon occurrence to the current level of activity, in which fine-needle aspiration specimens now represent 40% to 50% of the nonrenal diagnostic material examined by electron microscopy. This study documents the increasing importance of fine-needle aspirate-type specimens in the everyday operation of a diagnostic electron microscopy facility.