Adults were tested for the way in which they process four types of subject and object relative clauses. The results support an anti-interruption and anti-rearrangement constraint that has been proposed by Slobin. The reason why interruption and rearrangment of linguistic units is hard for adults is explained in terms of language-processing strategies that they are hypothesized to be using, in particular the Adjacency strategy. Adult behavior is compared to the performance of 4- and 5-year-old children in a previous study. The results of these two studies support the claim that children and adults are following the same strategies in processing these sentences, and that the difference between them is in which strategies they rely most heavily on, and, consequently, which sentences they make the most mistakes on.