In a three-way-crossover study in 18 healthy male and female subjects aged from 20 to 49 years the influence of a 1% and 3% solution of a standardized composition of Citrus limon, succus, and extract from Cydonia oblonga, fructus (Gencydo) on the intranasal mucociliar clearance was investigated after multiple administration. The pH of the solution was about pH 2.3-3.2. The dose regimen consisted of 20 puffs (0.13 ml per puff) in each nostril within 24 h, which was by factor 3-10 higher than the usual therapeutic dosage of 2-6 puffs per nostril and 24 h. The mucociliar transport time was measured by a modified saccharin test, where 1 microliter of a 3-molar aqueous sodium saccharinate solution was applicated at the inferior nasal turbinate 1 cm from its anterior end using a glass capillary microliter pipet. This test was performed at screening examination, before each administration period, directly after each 24 h treatment period and 24 h after the end of each treatment. The time of initial taste perception could be defined with high precision by the volunteer since it appeared very spontaneously. Neither after intranasal administration of the 1% and 3% Citrus/Cydonia solution nor after placebo solution a prolongation of the perception time was found. It could be concluded that there is no measurable influence of the test products on the intranasal ciliar function.