Two studies with 59 Ss (preschoolers–4th graders) explored the effects of stimulus factors on children's ability to monitor comprehension of messages as listeners in a referential communication situation. Results of Exp I show that both complexity of the stimulus array and degree of message ambiguity affected performances. In line with previous findings, 4th graders but not younger Ss showed evidence of effective comprehension monitoring. Data from Exp II show that when conducive stimulus conditions were arranged, even 1st graders demonstrated considerable skill in comprehension monitoring. In addition to investigating comprehension monitoring per se, the studies also examined the role of comprehension monitoring in directing the overall comprehension process.