Diseases are among the most important limiting factors in maize production in the American tropics, and ‘maize (corn) stunt’ has long been recognised as one of the major problems of the crop in this area. For several years the etiology of the disease was poorly understood, and several different symptoms were associated with maize stunt, which is now known to involve viruses and spiroplasmas. Rayado fino (Spanish for fine striping) virus (RFV) is presently recognised as a distinct pathogen within the maize stunt complex and has been shown to be responsible for the rayado fino disease, which is widespread and increasingly important in the American tropics. Symptoms, which are characterised by a fine chlorotic stipple striping of the leaf veins are generally mild, but reductions of yields are frequently appreciable. The cicadellid leafhopperDalbulus maidisDelong & Wolcott, is the most important vector of the virus in the American tropics, although other species of leafhoppers have been indicated in North America. Virus particles are icosahedral, 30 nm in diameter and contain single-stranded RNA. The virus is not serologically related to other isometric plant viruses. Both virus and vector possess a restricted host range, limited to maize and teosinte. Rayado fino is frequently found under widely different ecological conditions. The disease may be controlled through the use of tolerant genetic material.