Focal adhesion kinase (FAK) is a 125-kDa cytoplasmic tyrosine kinase located in cells which create attachments with the extracellular matrix (ECM) or with other cells. The primary function of FAK is to transmit the signal coming from the integrine receptor, participating in adhesion, to the intracellular protein cascade. The FAK kinase transducing the signal indirectly plays a crucial role in many cellular processes. This protein is engaged in cell cycle regulation, adhesion, migration, invasion and metastasis, cytoskeleton protein phosphorylation, and apoptosis. Deregulation of the FAK-dependent processes, e.g. adhesion, growth, viability, and cell mobility, is a significant element of cancer progression. FAK protein level expression is varies widely and depends on the development grade of the cancer. A minor FAK overexpression is already observed in the preinvasion grade, increasing significantly in the invasive state. The high FAK expression correlates with cancer cell migration, invasion, and ability for metastasis. The evaluation of FAK expression in cancer cells might become an important prognostic factor, since FAK expression studies provide important information that provides the opportunity to identify the cancer grade.