This invention relates to compositions comprising thalidomide and irinotecan, which can be used in the treatment or prevention of colorectal cancer. The invention also relates to methods of treating or preventing colorectal cancer which comprise the administration of thalidomide and irinotecan to a patient in need of such treatment or prevention. The invention further relates to methods of reducing or avoiding adverse side effects associated with the administration of irinotecan which comprise the administration of thalidomide to a patient in need of such reduction or avoidance.