Introduction: Olanzapine administered at a 10mg dosage for prophylaxis of chemotherapy-induced nausea and vomiting may be associated with fatigue, drowsiness and reduced general activity. Therefore, a 5mg dose may be preferred, to reduce the occurrence of adverse events. The aim of this study was to conduct a network meta-analysis, and report on the efficacy of olanzapine administered at 5mg, relative to when administered at 10 mg. Methods: We used previously-published data from the systematic review by Chow et al which identified 17 adult trials which used 10mg doses, 3 which used 5mg doses, and 1 which used a mix of 5 and 10mg doses. A multivariate network meta-analysis using a restricted maximum likelihood model was used. Results: The complete response rate in the acute phase is not statistically different, between 5mg and 10mg doses of olanzapine – RR 0.97, 95% CI: 0.83 – 1.13. Additionally, in the overall phase, 5mg olanzapine is similarly as efficacious as 10mg olanzapine – RR 0.95, 95% CI: 0.56 – 1.60. Evaluation of data demonstrated that there was inadequate information to compare the toxicities of the two doses. Conclusion: Our analyses support individual published trials, and the rationale for future trials to compare 5mg to 10mg olanzapine regimens in head-to-head comparisons.