Prevention of chemotherapy induced nausea and vomiting in an outpatient population requires an antiemetic regimen which is reliable and safe and easy to administer. In this study the use of oral ondansetron was investigated in 45 patients receiving 143 courses of non-cisplatin containing chemotherapy regimens on an outpatient basis. Complete control of emetic episodes was achieved in 79% of the courses (n=113/143), major control in 9.1% (n=13/143), minor control in 7.7% (n=11/143) and treatment failure in 4.2% of the courses (n=6/143). Nausea was less well controlled than emetic episodes. 53.1% (n=76/143) of the patients had no nausea, 24.5% (n=35/143) presented with grade 1 nausea, 16.8% (n=24/143) had grade 2, and 5.6% (n=8/143) had grade 3 nausea. The analysis of different groups of chemotherapy regimens according to the most emetogenic substance of a given regimen revealed, that 5-fluorouracil containing regimens were less well controlled then regimens with supposedly higher emetogenic substances. Delayed nausea but not emetic episodes were observed after 16.8% (n=24/143) of the courses indicating that this phenomenon may be a problem not only after cisplatin treatment. Side-effects following ondansetron treatment were obstipation (21%; n=30/143), sedation (11.9%, n=17/143) and headache (9.8%; n=14/143). Other side effects were less frequent and none of the side effects required treatment or discontinuation of the ondansetron administration. Outpatient treatment with ondansetron was effective, safe and well tolerated not ony in the first hemotherapy cycles but also in subsequent cycles.