The SemEval-2007 task to disambiguate prepositions was designed as a lexical sample task. A set of over 25,000 instances was developed, covering 34 of the most frequent English prepositions, with two-thirds of the instances for training and one-third as the test set. Each instance identified a preposition to be tagged in a full sentence taken from the FrameNet corpus (mostly from the British National Corpus). Definitions from the Oxford Dictionary of English formed the sense inventories. Three teams participated, with all achieving supervised results significantly better than baselines, with a high fine-grained precision of 0.693. This level is somewhat similar to results on lexical sample tasks with open class words, indicating that significant progress has been made. The data generated in the task provides ample opportunitites for further investigations of preposition behavior.