Clinical data analysis is a systematic effort to achieve a provisional diagnosis and ultimately a final complete diagnosis. The process will help to narrow differential diagnosis to least number of possible probabilities and to plan least number of investigations. Clinical data analysis requires knowledge, experience, analytic skill, and most importantly time to spend with patient. It also requires clinical expertise, a combination of scientific knowledge, and problem solving process. For better understanding of the complicated and ill-defined process, this chapter presents discussion on clinical data analysis in 10 steps which are helpful in day-to-day clinical practice. Some fundamental governing theories of clinical medicine are also covered in this chapter.