Despite considerable effort and expenditure by the Korean government and universities to promote technology use in tertiary education, few teachers of English in Korea regularly and consistently employ technology in their teaching. Moreover, research into the hindrances and enablers of technology use in English education in Korea has been limited for primary and secondary schools and conspicuously absent on the tertiary level. This case study examines what teachers in a general English department at a private university in Seoul undergo as they consider the use of technology both in and out of classrooms. It attempts to provide a holistic look into teacher decision-making in this context. It employs a grounded theory of investigation underpinned by a close reading of the diffusion of innovations theory by Rogers (2003). Data for the study involves three main techniques: semi-structured interviews, a survey questionnaire, and classroom observations. Analysis follows an iterative, grounded method and includes use of both qualitative and quantitative software programs (Atlas.ti 5.0 and SPSS 16.0 respectively). Results from the study form a substantive theory entitled "what works" which helps explain the myriad of decisions that teachers make while trying to manage personal (internal) and administrative (external) goals and aims. Further, all decisions within this system are underpinned by "what works" for teachers in any situation both in terms of reliability and consistency. Implications suggest that the use of technology in the classroom exacerbates preexisting pedagogical and infrastructure issues, leading to inconsistencies in representation and application, as well as an overall limitation of potential use by teachers.