 The Klein Laxative Tea is a pharmaceutical phytotherapeutic product thats been used for several years in Brazil for the treatment of constipation. This product contains fruit of Pimpinella anisum green anises, fruit of Foeniculum vulgare fennel, flowers of Sambucus nigra elder tree and flowers of Cassia angustifolia senna. In spite of the beneficial effects of its components, separately demonstrated in vitro, it never had its effectiveness appraised in a randomized clinical trial.The purpose of this study was to evaluate the efficacy and safety of this product in a randomized crossover placebo-controlled clinical trial. Twenty patients presenting with the criteria of the American Association of Gastroenterology for chronic constipation were included, and concluded a two-phase crossover study. The primary endpoint was the evaluation of the intestinal transit time measured through radiological technique. The secondary endpoints were the number of evacuations, subjective impression of the quality in the intestinal habit, quality of life appraised through WHOQOL-brief and adverse effects. 