This study investigated contextual guessing strategies employed by preintermediate students at Hacettepe University, Department of Basic English, and the different strategies used by successful and unsuccessful guessers when dealing with unknown vocabulary. Data were collected through an in-class reading task, thinkaloud protocols (TAPs) and retrospective interviews (RIs). The in-class reading task was administered to select three successful and three unsuccessful guessers. TAPs and RIs were conducted with the selected guessers to gather data on their strategy use. Transcribed TAPs and RIs were coded, and a contextual guessing strategies taxonomy was constructed. Frequencies and percentages for each strategy in the taxonomy and percentages for the participants’ guessing success in the in-class and TAP reading tasks were calculated. Findings of the study indicated that various strategies were employed to guess word meanings, and although both successful and unsuccessful guessers employed the same strategies, successful guessers used them less frequently. However, successful guessers’ arriving at more correct guesses provided evidence that they were more effective users of lexical inferencing strategies. Another finding illustrated that context and knowledge of the native language were the major sources for word guessing.