How well can children and adults understand complicated sentences ? How do their structure and mode of presentation influence our understanding ? To answer these questions, six sentences, two(differing in length) representing each of three different kinds of sentence structure, umekomi (chained active), ukemi (chained passive), and heiretsu (binary active) were prepared and each was given orally to a group of some 20 Ss. Elementary school pupils, studerits of junior high and high schools, and some university undergraduates served as Ss. Ss were asked to recognize the relationship among the names appearing in the stimulus sentence. The results show that the complicted sentences used in this eries of experiments, especially auditory ones, were too diflicult for even university students to cope with. Heiretsu was the easiest of the three. Most Ss could not parse properly the more complicated sentences of umekomi and ukemi. and tended rather to regard them as sets of gra-mmatically incomplete simple sentences. This tendency could be trace through all age-levels of Ss, and there were no qualitative differences among the processing strategies Ss had adopted. Visually pre-sented, however, the stimulus sentences were understood fairly well by elementary school pupils. The strategies for processing aurally presented sentences seem to depend heavily on the inflected form of the first "auxiliary verb", the function of which was grasped somewhat ungrammatically by most of the Ss.