Chapter 2 deals with the various types of Research Study Designs used for biomedical research. It deals with the routinely used observational methods falling in the descriptive as well as analytical category, and also the experimental ones. Newer, and now more frequently used study designs, viz. the quasi experimental design, hybrid designs (e.g. nested case-control, case-cohort) and various types of qualitative designs (e.g. case study, observations, in-depth interviews, focus groups) have also been included in the discussion. The latest technique being used in research, namely the systematic reviews (or the so-called meta-analysis). Naturally, trying to put in so much has made this chapter a bit lengthy.