Interferons alpha, beta and gamma (IFN) were initially identified as soluble factors able to inhibit infection of chick chorioallantoic membranes by influenza A virus. Although the mechanism(s) of action of IFNs are unclear, these molecules express their biologic properties after binding to specific high-affinity cell membrane receptors. To dates several clinical studies have challenged the therapeutic benefits of using IFNs in the treatment of solid tumours and haematologic malignancies. The reported results have shown a wide range of response rate, and toxicities in general are manageable, predictable and rarely of major clinical significance. These studies have also raised the interesting possibility for improving cancer treatment with combination of IFNs and conventional anticancer regimens, or combinations of IFNs with other Biological Response Modifiers (BRMs), such as interleukin 2. Hopefully, this area of research will lead to an entire rethinking of the use of our existing anticancer treatment modalities, which perhaps could lead to solutions to old clinical problems.