This study investigates the effect of interaction on the comprehension of input containing new lexical items and the acquisition of these new lexical items. Fourteen kindergarten English as a second language (ESL) students and a native-English-speaking teacher participated in the study which incorporated a pretest-posttest design in two rounds. All subjects completed the pretests and posttests. An experimental group of 11 subjects participated in four communication tasks (one individual task and one group task in each of the two rounds) which comprised the treatment phase of the study while the remaining 3 subjects formed the control group. New lexical items were embedded in the task instructions. As a result of each communication task, each subject received an interaction score based on the number of negotiations for the meanings of new lexical items he or she initiated. The comprehension score was based on the degree to which the task was successfully completed. The acquisition score was obtained by comparing pretest and posttest results. The results reveal that the amount of interaction the subjects initiate is significantly, but inconsistently, related to comprehension but appears to be unrelated to acquisition. Furthermore, comprehension appears to have no effect on subsequent acquisition which, however, does take place. The results support the claim that negotiated interaction can facilitate comprehension. However, this is tempered by evidence, also found in the present study, which supports the claim that teachers' elaborations can confuse learners and impede comprehension. Finally, the results offer confirming evidence for the claim that classroom interaction can facilitate comprehension for those learners who are exposed to the interaction as well as those learners who actually engage in the interaction.