This paper discusses the results of two questionnaire surveys which are designed to find out how Korean college students perceive some problematic English sentences and how their imperfect knowledge of English grammar affects their attitudes towards speaking English. The major purposes of the paper are: first, to analyze what erroneous sentences they find either correct or incorrect; second, to find out how much they can be lenient with problematic Eng lish sentences by analyzing what sentences they think are fine to understand and would use; third, to investigate how their lack of proper knowledge of English grammar affects their attitudes in using and learning English; and fourth, to discuss importance of grammar teaching in an EFL classroom. In line with recent studies on World Englishes, this research adheres to the idea that it is significant to give students opportunities to use the language without fear of making grammatical mistakes rather than emphasizing Standard English and the correct language. However, the results of the surveys show that the lower the level of their English proficiency, the more they want to speak grammatically correct English, and the lesser they show leniency towards deviant English structures.