An online picture description methodology was used to investigate the interaction between lexical and syntactic information in spoken sentence production. In response to arrays of moving pictures, participants generated prepositional sentences, such as "The apple moves towards the dog," as well as coordinate noun phrase sentences, such as "The apple and the dog move up." In Experiments 1 and 2, speakers produced the same sentence structures on prime and target trials. In addition, a pictured object was repeated in either similar or different sentence positions. Lexical repetition speeded sentence production when it occurred on the first item of the target sentence (Experiments 1 and 2). However, priming was dependent on the structural position of the to-be-repeated word in the prime sentence. In particular, a noun that occurred in a prepositional phrase did not result in facilitation when it was repeated as the head of the subject phrase (Experiment 1). This effect was shown to be independent of differences in the linear position of the repeated word in prime and target trials (Experiments 2). Experiments 3 and 4 demonstrated that lexical repetition returns when the effect of sentence structure is removed. Possible mechanisms for this interaction between lexical and structural repetition are explored. (Contains 5 tables.)