There is considerable variation in the prevalence of comorbid conditions such as malnutrition, inflammation, cardiovascular disease, and bone disease among end-stage renal disease (ESRD) patients on maintenance hemodialysis. Besides traditional risk factors, these differences also arise from variability in genetic factors and gene-environment interactions. Recent publication of the human genome sequence through the Human Genome and Celera projects has provided a major impetus to the field of molecular genetics and genomic medicine. This review provides a broad overview of recent developments in this field, basic information and terminology in common use, and explores the impact of genetic variations or polymorphisms on human biological diversity.