This study evaluated the effectiviness and the onset of action of levocabastine (CAS 79547-78-7) nasal spray and eyedrops as well as of nedocromil (CAS 69049-74-7) nasal spray and eyedrops in practical relevant circumstances. The study was designed as an open observational study with parallel groups in 10 centres and comprised 102 patients. All patients presented with seasonal allergic rhinitis and evidenced conjunctival symptoms requiring therapy. The patients as well as the investigators were required to rate the symptoms using symptom scores in order to evaluate the effectiveness of the used drugs. The effectiveness according to symptom scores did not differ significantly between investigator's and patient's judgment. Onset of action was within the first hour in 81.6% of the patients treated with levocabastine and in 82.9% of the patients treated with nedocromil. Symptoms were evaluated on a visual analogue scale ranging from 0 to 100. The use of both substances reduced the severity of the reported symptoms by 50% within the first hour. Thus, no significant difference in the onset of action could be observed even though a later onset of action was expected of the stabiliser of mast cell membranes. Both drugs were tolerated well.