The basic principle of pupillometry is to measure the changes of pupillar++ diameter versus time. We used a special device: split lam stand, black and white television camera with monitor fixed to a Polaroid. Trospium chloride is a compound with anticholinergic efficacy. The injection of 0.8 mg of trospium chloride followed by oral administrations of 10, 20, and 40 mg showed increasing effects on the mydriatic reaction. Comparing the area under the curves made it possible to estimate the bioavailability of the compound.