The development of biological drugs, which began in the 1980s, has revolutionized the treatment of numerous oncological diseases and severely disabling autoimmune diseases, with widely demonstrated evidence of benefit. Today, biological drugs represent an important and continuously developing category and are used both as a support therapy in onco-hematology and as molecules with their own therapeutic activity, such as monoclonal antibodies. Among these, bevacizumab represents a drug of relevant clinical value, used as antiangiogenic therapy in numerous cancers, in particular colorectal and ovarian cancers. The expiry of the patent period of monoclonal antibodies, including bevacizumab, has opened up to the development of biosimilar drugs, represented by structurally similar molecules with pharmacokinetic, pharmacodynamic and clinical characteristics equivalent to a biological drug already present in clinical use (originator biologic). The development process of these drugs is contained in the guidelines of the major regulatory bodies (FDA/EMA) and is faster than that provided for the originator biologic. Since biosimilars have a lower cost than reference drugs, their use represents a possibility of containing health care costs and of satifying the growing demand in terms of efficacy and personalization of pharmacological therapies. Considering the particular severity of the diseases treated, including colorectal and ovarian cancers, biosimilar drugs must be used with full awareness, in terms of efficacy and safety, since their approval is based on a rigorous analytical process, as well as preclinical and clinical evaluation.