Twenty-six domestic reports of suspected adverse reactions from the guar gum-containing diet pill, Cal-Ban 3000 (filed with the FDA) were reviewed. There were 18 instances of esophageal obstruction, seven instances of small bowel obstruction, and one individual who was reported to have died after ingestion of Cal-Ban 3000, but for whom insufficient details were provided to assess causation. There were 14 women and 11 men (mean age 46.3 yr; range 17 to 67 yr) for whom sufficient information was available. Preexisting esophageal or gastric disorders were present in 50% of those with esophageal obstruction, including peptic stricture, pyrosis, hiatal hernia, esophagitis, gastric stapling procedure, Schatzki ring, and muscular dystrophy. Fourteen of these 18 patients with esophageal obstruction were treated successfully by endoscopy, although the tenacious gel-like consistency of the material was often difficult to remove. Two patients required rigid esophagoscopy when flexible endoscopy was unsuccessful. This resulted in the death of one patient who developed a pulmonary embolism after surgical repair of an intraoperative esophageal tear. For the seven patients with small bowel obstruction, no specific predisposing factors were mentioned. One individual required exploratory laparotomy, and inspissated tablets were found in the ileum. These cases, spontaneously reported to the FDA, are very similar to those reported in the literature. The water-holding capacity and gel-forming tendency of guar gum permits it to swell in size 10- to 20-fold, and may lead to luminal obstruction, especially when an anatomic predisposition exists. Such products have been banned in Australia, and Cal-Ban 3000 has recently been removed from the market in the United States. However, unsuspecting patients who are still in possession of the product should be apprised of the potential complications that may arise with its use.