The utility of on-site microscopic evaluation of fine needle aspirates (FNAs) of the head and neck was assessed by comparing the diagnostic yield in 336 specimens obtained with immediate on-site cytopathological procurement and evaluation to that achieved in 548 cases performed without immediate on-site evaluation. Three hundred six (91%) of 336 immediate evaluation specimens were adequate for cytopathologic diagnosis, compared to 391 (71%) of 548 specimens not evaluated immediately (P < .001, chi-squared test). The higher satisfactory rate in immediate evaluation cases was related primarily to 1. immediate reaspiration of the masses until sufficient cytopathologic material was obtained for diagnosis; and 2. optimal specimen preparation. It is concluded that immediate on-site cytopathological procurement and evaluation of fine needle aspirates of head and neck masses is a valuable practice which assures a higher yield of adequate specimens compared to biopsies taken without immediate evaluation. The technique of immediate on-site evaluation of FNAs is discussed and a cost-benefit analysis of immediate on-site evaluation of FNAs is presented.