SPECT method is used to analyze changes in regional cerebral blood flow in a group of 19 normal subjects during a baseline task (repetition of two words) and two verbal fluency tasks, a semantic fluency and a formal fluency. The semantic fluency task was associated with a relative CBF increase in the right dorso-lateral and medial frontal region when compared with that seen in the baseline condition. No specific activation was found for the formal fluency task compared to that seen in the baseline task. We suggest that the activation of the right frontal region reflects semantic categorization strategies in semantic fluency. The lack of activation of the left frontal region may be due to an activation induced by the nature of the baseline task (i.e., a self-paced repetition task).