The clinical efficacy of polycarbophil calcium was assessed in 57 patients of both sexes aged between 18 and 77 years old affected by chronic non-organic constipation. The multicentre study was performed using a single blind and cross-over protocol for 8 weeks, 4 with placebo and 4 with the drug (2 c.p.s 3 t.i.d). Thirteen patients failed to complete the study, 8 of them for reasons not related to the drug. In comparison to placebo, the drug caused a significant reduction in the consistency of stool and evacuatory force during the first week of stool therapy. Medical judgement was that efficacy was "very good" in 73% and "good" in 18%, whereas the drug was thought to be "non efficacious" in 9% of cases. The statistical analysis of data confirmed the efficacy of the drug. The hematochemical parameters evaluated before, during and after treatment only showed a slight increase in calcemia and calciuria which did not reach statistical significance. The therapeutic efficacy and lack of undesired effects confirm the value of polycarbophyl calcium in the treatment of chronic constipation