Abstract： Objective To investigate the factors influencing the prognosis of the patients with malignancies involving the infratemporal fossa and parapharyngeal space.Methods 73 patients with malignancies involving the infratemporal fossa and parapharyngeal space were reviewed retrospectively.All patients underwent operation with adjuvant radiotherapy ( n =30) and chemotherapy ( n =9).Kaplan - Meier method was used to analyze the survival and Logrank test was used to Compare the difference between two groups.Multivariate analysis was performed by Cox proportional hazard model.Results The overall 5 - year survival,cancer - specific survival and progression - free survival rates were 46.7％,51.5％,40.6％ respectively.The univariate analysis showed that the relationship of tumor and skull base,tumor grades,surgical margins,tumor sizes were associated with cancer - specific survival and progression - free survival simultaneously.While the gender and pathologic types were only associated with progression - free survival.Multivariate analysis indicated that tumor size was an important independent prognostic factor.Conclusions Tumor size is an important and independent prognostic factor for malignancies involving the infratemporal fossa and parapharyngeal space.