Major difficulties in planning treatment of laryngeal cancer are the assessment of three dimensional volume of the tumor, its extent of submucosal spread, and its possible destruction of the thyroid and cricoid cartilages that the laryngeal framework. Invasion of the framework is an adverse prognostic feature associated with an increased incidence of regional metastasis and decreased survival. It has been well known that laryngeal cartilage invasion is restricted to the ossified portion. The reasons still remain unclear in spite of an extensive array of experimental work. Thirty laryngectomy specimens were sectioned serially and reviewed histopathologically to investigate the patterns and mechanisms of the laryngeal cartilage invasion, and to assess the predictability of CT for the detection of laryngeal cartilage invasion through a comparison of CT images with pathologic serial sections. The obtained results were as follow : 1) The thyroid cartilage was most commonly invaded, followed by arytenoids, cricoid and epiglottic cartilage in order. The incidence of cartilge invasion was high in transglottic cancer. 2) There was no statistical significance between cancer cell differentiation and cartilage invasion(p>0.05). 3) Laryngeal cartilge invasion chiefly occurred in ossified portions. The nonossified cartilage was invaded very rarely with minimal invasion in extensive lesion. 4) The accuracy rate of CT was 72.0% in arytenoid, 88.0% in cricoid, 92.0% in epiglottic cartilage. Negative predictability of CT for cartilage was high but positive predictability was low. In conclusion, the mechanisms of cartilage invasion could be summarized as spread of cancer cell through collagen bundles in soft tissue and bone destruction by osteoclastic reaction is ossified cartilage. This suggests that invasion is largely indirect process dominated by local bone destruction with osteoclasts operation in front of the advancing tumor. Once ossified cartilage was invaded by cancer cell, they spread through narrow space in the presence of intact perichondrium and left pitfalls in performing a partial laryngectomy. Perichondrium was a strong barrier to cancer invasion. Diagnosis of the laryngeal cartilage invasion is difficult because the process of ossification of laryngeal cartilage is entirely unpredictable. These results indicate that CT correlates with anatomic location of gross cartilage invasion, however, small macroscopic and microscopic invasion of the laryngeal cartilages is difficult to diagnose with CT. Decisions regarding conservation surgery cannot be based on CT evaluation alone.