The purpose of this review is to discuss recent literature data concerning the etiology and pathobiology in insulin-dependent diabetes mellitus as well as present our own experience from all children up to 15 years of age in Uppsala County, Sweden presenting with juvenile (type I) diabetes since 1976. Chronic enterovirosis is an emerging concept in apparently immunologically competent patients. By means of new serological and DNA-based methods, a persistent enteroviral (Coxsackie virus A, B and ECHO virus) infection can sometimes be demonstrated after an acute primary infection, which is often subclinical. There are several indications that these viruses can contribute to the development of illnesses with a pathogenesis as yet not fully understood, e.g. dilated cardiomyopathy, type I diabetes, and possibly some cases of the so-called chronic fatigue syndrome. In type I diabetes, many pieces of evidence including epidemiology, genetic analysis of the host susceptibility genes, cytokine analysis and new seriological evaluation suggest an infection to be the starting point for the beta cell destruction. These etiological agents most likely belong to the enteroviral group of picornaviruses. Later events may well involve all parts of the immune system launching a selective autoimmune 'suicidal attack' on the cells necessary for glucose homeostasis.