Our objective was to determine the efficacy of adding acarbose to the combination of metformin and a sulfonylurea in the treatment of type II diabetes mellitus. Acarbose was added to the treatment regimen of 11 type II diabetic patients who were not adequately controlled on the combination of a sulfonylurea and metformin. Glycosylated hemoglobin before and after the addition of acarbose was compared to assess the efficacy of this additional therapy. One patient did not tolerate acarbose therapy. Of the remaining ten patients, the mean improvement in glycosylated hemoglobin with the addition of acarbose was 1.4 percentage points, p = 0.01. Eight patients had improvements in glycosylated hemoglobin; mean improvement, 2.0 percentage points. Two patients' glycohemoglobin values worsened. Thus, the addition of acarbose to the treatment regimen of type II diabetic patients presently on a combination of a sulfonylurea and metformin improves glycemic control.