This research is focused on analyzing the studentsâ ability in masteringconditional sentences. Population of this research is the students of Faculty ofLetter at Second Grade in Gunadarma University in the academic year of 2007â 2008 whereas 40 of them are taken as sample, to be taken randomly. Toconduct this research the writer used descriptive quantitative research toanalyze the ability of the students of Faculty of Letters in mastering conditionalsentences. Based on the analysis, the percentage of errors in understandingconditional sentence are 30,42% in type I, 68,57% in type II, and 67,85% in typeIII. So, it means that the student find difficulties in understanding conditionalsentences in type II and type III. The result of this research showed that mostof the students performed unsatisfactorily. Most of them got less than 60% ofcorrect items. It means that their English are still poor and they have difficultiesto master conditional sentences.