We report a patient with transcortical sensory aphasia (TCSA) following a left frontal lesion. The patient was a 63-year-old right handed Buddhist priest admitted to our hospital with a complaint of word-finding difficulty. Neurological examination failed to reveal any abnormal findings except aphasia. The patients spontaneous speech was fluent, not agrammatic, and free of phonemic paraphasia but he sometimes exhibited semantic paraphasia. His ability to repeat sentences was excellent, but he had severe difficulty in word-finding, auditory comprehension and writing. He read aloud correctly, but his reading comprehension of kana (phonograms) was poor in contrast to excellent reading comprehension of kanji (morphonograms). His clinical picture was characterized by poor comprehension but excellent repetition, and a diagnosis of TCSA was made. CT and MRI revealed an infarction involving the pars opercularis and pars triangularis in the inferior frontal gyrus and the anterior portion of the lower prefrontal gyrus and the middle frontal gyrus. Regional cerebral blood flow was measured by single photon emission CT and was found to be decreased in the same region as indicated on CT and MRI. The clinical picture in this patient was comparable to that of TCSA due to a posterior parieto-occipital lesion, but the rapid improvement (within 1 to 2 months) of this patient was characteristic. Auditory comprehension, kana (phonograms) reading comprehension, and word recall, which were severely impaired in this patient, all demand interaction between phonological processes and semantic processes. Thus we conclude that this patient had impairment of the phonological-semantic interaction process.