OBJECTIVE To estimate the incidence and to evaluate risk factors for antineoplastic nausea and vomiting with high and moderate emetogenic chemotherapy in adult patients in the first treatment cycle. METHODS Prospective cohort study with follow-up of 269 adults during the first cycle of antineoplastic chemotherapy. The incidence of nausea and vomiting was evaluated in the acute phase (0-24 hours), in the late phase (24 hours-5th day) and in the total phase (0-5th day). RESULTS In total, 152 patients underwent high emetogenic chemotherapy and 117 moderate emetogenic chemotherapy. The relative frequency of nausea was higher when compared with vomiting in the acute phase (p < 0.001) and in the late phase (p < 0.001). The risk factors identified were: age group ≤ 49 years (odds ratio = 0.47; 95%CI 0.23-0.95) and 50-64 years (odds ratio = 0.45; 95%CI 0.23-0.87), tobacco use (odds ratio = 0.35; 95%CI 0.14-0.88), and high emetogenic chemotherapy (odds ratio 0.55; 95%CI 0.31-0.95). CONCLUSIONS The incidence of nausea was higher than that of vomiting, and adverse effects were more frequent in the late phase. The results suggest the risk factors for chemotherapy-induced nausea and vomiting are tobacco, age (young adults), and high emetogenic chemotherapy.