In man, the early metabolic abnormalities associated with diabetes mellitus are followed by various long-term complications1. The cause of these complications is not clear, but they may be secondary to persistent abnormalities in blood glucose levels2. In mice, several viruses can infect and destroy pancreatic β cells and produce acute-onset insulin-dependent diabetes mellitus (IDDM) characterized by hypoinsulinaemia, hypergly-caemia, glycosuria, polydypsia and polyphagia3. The virus most studied is the M variant of encephalomyocarditis (EMC) virus4,5. Long-term complications, however, have been difficult to demonstrate because in most mice, the diabetes is transient and mild. Recently, by plaque purification, we have shown that the M variant of EMC virus actually has two stable variants: one diabetogenic (designated D) and the other nondiabetogenic (designated B). Further studies revealed that the B variant reduces the severity of the diabetes produced by the D variant6. We now report that when mice are inoculated with the D variant alone, many develop severe and prolonged hyperglycaemia followed by some of the long-term complications of diabetes, including reduced lifespan, glomerulosclerosis and ocular changes.