Both genetic and environmental factors have been implicated in the mechanism of various disorders. Epidemiological data have shown that environmental factors can also cause and/or exacerbate the pathogenesis of these diseases. However in this article, we provide a summary of evidence for environmental and genetic factors influencing the diseases. The review also incorporates the major findings categorizing the common diseases on the basis of genetic profiles and ethnic information and in establishing personalized disease diagnosis, drug responses and treatment modalities based on the genetic determinants. These studies provide important insights into the interplay between environmental and genetic factors leading to human diseases. Overall an attempt has been made to highlight the importance of studying the genetic profiles of an individual with many factors.