Evidence currently available suggests that in established, progressively growing solid tumours, tumour associated macrophages (TAMs) are reprogrammed to induce immune suppression of host defenses in situ, through release of specific cytokines, prostanoids and other humoral mediators. This disordered response, results in the inhibition of effective anti-cancer cell-mediated immune mechanisms. Concurrently, TAMs produce tumour growth promoting factors. The summation of this complex interplay of biological factors results in progressive tumour growth and tumour cell dissemination. A better understanding of these complex inter-relationships should form the basis of novel strategies designed to eradicate tumour cells in man and animals. These various biological aspects and processes are discussed in detail and critically evaluated in this review article.