Patients with cancer may receive chemotherapy that may cause nausea and vomiting. The purpose of this study is to determine if the use of olanzapine in combination with antiemetic therapy can significantly reduce nausea and vomiting in a large number of patients receiving chemotherapy. Patients are randomized to one of two treatment arms. Please see the "Arms and Intervention" sections for more detailed information. The primary objective is to compare the number of patients with no nausea for the acute (0-24 hours post-chemotherapy), delayed (24-120 hours post-chemotherapy) and overall periods (0-120 hours post-chemotherapy) for patients receiving HEC. The secondary objectives are:
1. To compare the complete response (CR) (no emetic episodes and no use of rescue medication) in the acute, delayed and overall periods
2. To compare the incidences of potential toxicities ascribed to olanzapine
Protocol treatment is to begin ≤ 14 days of registration. Patients will receive treatment on Days 1-4. Patients will be permitted to take rescue therapy of the treating investigator's choice for nausea and/or emesis/retching, based on clinical circumstances. After completing treatment, patients will be monitored for side effects.