Background: Chemotherapy induced nausea and vomiting (CINV) following carboplatin containing chemotherapy regimen remains a considerable problem for cancer patients (pts) despite standard antiemetic prophylaxis. This study was undertaken to prospectively evaluate the incidence of CINV in pts undergoing carboplatin-based chemotherapy receiving guidelines consistent CINV prophylaxis (GCCP). All sites did not prescribe NK1-RA as it is not included in all institutional guidelines. Methods: The study enrolled 207 pts undergoing carboplatin-based chemotherapy, the final analysis evaluated cycle 1 - 6 with a total of 183 evaluable pts from 6 countries. Pt diaries were used to collect data from day 1-10 beginning with cycle 1. Nausea was reported by the pts using a visual analog scale (VAS) with the end-point being no nausea. Vomiting episodes were recorded in the pts’ diaries. Demographic, occurrence and severity of emesis, numbers of emetic episodes and time to the onset of emesis, were summarized using descriptive statistics. Results: There were 129 females and 54 males. The overall incidence of acute and delayed nausea for was 17% and 25% respectively. The incidence of nausea of entire population was significantly higher than vomiting (58% vs. 14%; Chi² 22.271 p<0.000). The use of NK1-RA was associated with a significant decrease in time to first vomiting for cycle 1 (p<0.041) and subsequent cycle 2-6 (p<0.0075). Additional results are reported in the Table. In a logistic regression model factors associated with acute nausea in cycle 1 included history of motion sickness (p< 0.0090), comorbidities (p< 0.0084), history of morning sickness (p< 0.0090), previous chemotherapy (p< 0.0096), anemia (p< 0.0209). A separate logistic regression analysis for delayed nausea in cycle 1 showed that prior radiotherapy (p<0.0093) and a history of morning sickness (p<0.0195) were also significant. During subsequent cycles (1 – 6), the incidence of nausea remained higher than vomiting and was documented in the acute and delayed phases ranging from 6% to 25%. The use of NK1-RA was associated with a lower incidence of vomiting during cycle 1-6 with 91% patient receiving NK1-RA experiencing no vomiting vs 78% of patients not receiving NK1-RA with no vomiting (log rank = 0.0287). Conclusions: Despite GCCP and the usage of NK1-RA, carboplatin induced nausea remains a major unmet medical need in cancer pts. Further research should focus on management of nausea, risk factors and the impact of nausea on quality of life and in pts undergoing carboplatin-based treatment.