In recent years, the interest in developing micro-electro-mechanical systems (MEMS) for biological and medical applications (BioMEMS) has drastically increased due to the impressive developments in the field of molecular biology, medicine, biochemical and material sciences as well as in microsystems technology. BioMEMS are extensively applied in diagnostic research, drug delivery, therapeutics, tissue engineering, biosensors and lab-on -a-chip systems. This paper focuses on BioMEMS applied in diagnostics such as the study of DNA, cells, proteins and viruses in lab as well as in point-of-care conditions and describes recent achievements in this important field. The future directions and prospects are also discussed. Miniature diagnostic devices are considered to dramatically increase the sensitivity of several test routines, and therefore the reliability of the diagnosis improves while the costs are reduced. Additionally, a step towards point-of-care diagnostics is achieved by BioMEMS development since the possibility of developing a system that integrates an entire test system in an affordable hand-held device is increased.