This qualitative instrumental case study explores various factors that might influence upper-intermediate-level English as a second language (ESL) students' summarizing from a sociocultural perspective. The study was conducted in a formal classroom setting, during a reading and writing class in the English Language Institute at a university in the southeastern United States. Seven international ESL students provided information through questionnaires and interviews. Additional data were gathered through classroom observation. The findings of the study provide evidence that such personal factors as culturally influenced thinking patterns, content knowledge, motivation and attitude, and native language and second language literacy skills, as well as textual factors, writing style, vocabulary, and grammar, have an effect on ESL students' summarizing.