An investigation using questionnaires was conducted to find clues to determine the existence of a hierarchical structure for descriptive adjectives having timbre. One hundred sixty-six subjects rated frequency of use for 114 adjectives having timbre on a seven-point scale. Based on the results of the subjective ratings, 50 descriptive adjectives were selected. One hundred sixty subjects then rated their subjective impressions of these adjectives by the following four scales: (1) concrete--abstract, (2) simple--complex, (3) objective--subjective, and (4) difficulty in recalling the expressed timbre. Similarity of the expressed timbre was also measured using a sorting method. The results were analyzed by MDS and clustering techniques. A hierarchical structure for the descriptive adjectives having timbre was interpreted from the results of the analyses. This research should form a basis for further investigation of a human timbre perception mechanism.