The present invention provides a method of treating a neoplasm using a neurotoxin, preferably botulinum toxin. Neurotoxin administered around a neoplasm acts to decrease the contractile forces of the muscles surrounding a neoplasm which normally squeeze neoplastic cells through efferent channels leaving the neoplasm to distant sites. The present invention also provides a method of administering botulinum toxin at sites distant from the neoplasm, thereby enhancing cellular and humoral immunologic functions, which further contribute to neoplastic cell death. Following administration of botulinum toxin around or distant to a neoplasm as described herein, local, regional, and distant spread of neoplastic cells is reduced or eliminated. Immunomodulation with botulinum toxin is also valuable in treating other diseases that may or may not be associated with cancers, such as viral-induced growths, viral conditions, fungal disease, chronic wounds, graft versus host disease, autoimmune disease, and HIV.