Calcium polycarbophil is the calcium salt of polyacrylic acid crosslinked with divinyl glycol. It is chemically and physiologically inert. In dilute alkali it possesses marked hydrophilic capacity (60 to 100 times its weight), which is the basis for its therapeutic use. In daily dosages of 4 to 5 g in adults, it appears to be quite safe, is non‐toxic, does not interfere with digestion or absorption, and does not cause gastrointestinal irritation. It appears to be effective in the treatment of both constipation and diarrhea due to functional or organic causes. Several days of continuous use are necessary before effectiveness becomes apparent. Clinical studies, of which there are relatively few, range from uncontrolled, unblinded evaluations of an almost anecdotal nature to well controlled, double‐blind, crossover studies. Additional carefully controlled studies on dietary influences, exercise, and patient compliance would be helpful. Adverse effects, which are minimal, include epigastric fullness or heaviness, abdominal distention and bloating, and flatulence. As with all bulk‐forming agents, calcium polycarbophil should not be used by persons who have stenotic lesions of the gastrointestinal