Polyomaviruses and Human Diseases -- Discovery and Epidemiology of the Human Polyomaviruses BK Virus (BKV) and JC Virus (JCV) -- Phylogenomics and Molecular Evolution of Polyomaviruses -- Virus Receptors and Tropism -- Serological Cross Reactivity between Polyomavirus Capsids -- Molecular Genetics of the BK Virus -- Serological Diagnosis of Human Polyomavirus Infection -- Human Polyomavirus JC and BK Persistent Infection -- Immunity and Autoimmunity Induced by Polyomaviruses -- The Pathobiology of Polyomavirus Infection in Man -- Polyomavirus-Associated Nephropathy in Renal Transplantation -- BK Virus and Immunosuppressive Agents -- BK Virus Infection after Non-Renal Transplantation -- Latent and Productive Polyomavirus Infections of Renal Allografts -- Urine Cytology Findings of Polyomavirus Infections -- Diagnosis and Treatment of BK Virus-Associated Transplant Nephropathy -- Pharmacotherapeutic Options for the Management of Human Polyomaviruses -- Leflunomide in Solid Organ Transplantation and Polyoma Virus Infection -- JC Virus Can Infect Human Immune and Nervous System Progenitor Cells -- The Polyomavirus, JCV, and Its Involvement in Human Disease -- Transforming Activities of JC Virus Early Proteins -- Polyomavirus in Human Cancer Development -- BK Virus, JC Virus and Simian Virus 40 Infection in Humans, and Association with Human Tumors -- Epidemiologic Studies of Polyomaviruses and Cancer. Science never solves apr oblem without creating ten more Geor ge Bernard Shaw How prophetic the above words prove to be when applied to the advances of 20th century medicine. Prior to Banting and Best, chnicians were unaware of the ravages of diabetes, patients simply wasted away and died. Following the purification of insulin, clinicians now had to deal with diabetic retinopathy, diabetic nephropathy and all the other complications of long-term diabetes. A little over 50 years ago, the first successful human kidney transplant was performed in Boston. The first 30 years of the experience had successes when compared to the alternative but were a constant struggle to get even 50% of the grafts from deceased donors to survive more than a year. However, the science continued to advance knowledge of the immune response. With this came more and increasingly powerful tools for the clinician. Suddenly, success rates of 80-90% at one year were attainable. With this success came new problems, new complications and clinicians now had to worry about the long-term consequences of their therapy as patients were surviving with functional grafts for extended periods. A particular infectious complication evolved with the application of ever more powerful immunosuppressant drugs. Astute clinicians noted that occasionally cellular rejections seemed to get worse with steroids. Despite their best efforts and the use of powerful drugs, patients lost their grafts to overwhelming interstitial infiltrates not seen before.