&NA;The bowel sounds of 21 patients with mechanical obstruction of the intestine were studied. A computer analysis of bowel sounds was performed using a signal processor. Bowel sounds of patients were classified into 3 types (Types I, II, and III) based on the histograms, although these were not distinguishable on auscultation. The lower, peak, and upper frequencies were 173 ± 25 Hz, 273 ± 64 Hz, and 667 ± 58 Hz, respectively, in Type I; 309 ±121 Hz, 632 ± 94 Hz, and 878 ± 116 Hz, respectively, in Type II; and 330 ± 120 Hz, 612 ± 86 Hz, and 766 ± 82 Hz, respectively, in Type III. High frequency sounds above 900 Hz were recorded in Types I and II but not in Type III. The ratio of the operated patients was 0, 23, and 100 percent in Types I, II, and III, respectively. The intervals between the times of admission and operation were 4.3 days and 1.2 days in Types II and III, respectively. Thus, it appears that the methods described by the authors could provide a very objective assessment of the severity and help determine the treatment (conservative or operative) of each patient.