This experiment investigated the reactive effects of verbal reports on spatial mental models. Participants studied a map marked with a route and then either verbalized their memory for the route or engaged in an unrelated verbal activity. Results showed that verbalization hindered performance on a measure of configural knowledge (straight-line distance estimations) but had no overall influence on a measure of featural knowledge (route distance estimations). In addition, verbalization differentially interacted with verbal ability on the memory measures. The implications for research on memory for spatial environments and the evidence for the existence of two distinct forms of memory representations (route versus configural) in spatial mental models are discussed. Copyright © 2002 John Wiley & Sons, Ltd.