This short review aimed to give to reader's brief applications of polymer colloids in biomedical area such as therapy and medical diagnosis as also developed in our laboratory. Indeed, the polymer particles and composite particles are commonly used in immunoassays as solid phase supports, for the encapsulation of active agents and for the immobilization of biomolecules such as oligonucleotides, proteins or antibodies. In the area of composite particles, magnetic particles bearing immobilized biomolecules are used in biomedical diagnosis such as immunoassay, specific nucleic acids concentration, cell labelling and separation and in numerous biotechnological applications.