The traditional methods of prevention, diagnosis and treatment of a disease are associated with a variety of pitfalls indiagnosis and mild to severe drug-related adverse effects. Most physicians prescribe a drug, change its dose or even thedrug by a ‘trial and error’ process because it is poorly understood why certain drugs do not work for some patients or whythey induce serious adverse effects in others. Personalized medicine is a concept that emerged with the completion of theHuman Genome Project and conveys information about a person’s genome, proteome and environment. Since these factorsare different for every person, nature of the disease including its onset, course and response to drugs also differs fromperson to person. The present review highlights the pros and cons of personalized medicine with special emphasis on thelikelihood of its impact on autoimmune diseases and cancer