The purpose of this paper is to investigate the usage of address terms between professors in a Korean university upon the methodology of sociolinguistic variation studies. This study was conducted based on on-line questionnaire survey targeting 100 professors in an university situated in the metropolitan area. Address terms observed in this study are Gyosu(=professor)(+honorific ‘-nim), Seonsaeng(=teacher)(+’-nim’), Baksa(=doctor)(+‘-nim’), Saem/Ssaem(intimate abbreviation of Seonsaeng), etc. which are ordered by frequency. Factor groups considered in this study are addressor, addressee, and situation. The main results of this study are as in the following. (1) Addresser’s academic field, degree of intimacy relation with addressee, and addressee’s administrative position are main factors having influence on the usage of address terms between professors. (2) Addresser’s sex and age factors and addressee’s sex and academic field factors have little or no influence on the usage of address terms.