Stroke-in-progression or stroke-in-evolution or progressing stroke is a clinical entity which is frequently encountered in several major types of stroke possibly even more frequently than the classical abruptly completed stroke. Stroke-in-evolution is in fact a mosaic or constellation of conditions including various causes (large infarcts, lacunes, distal fields infarcts, hemorrhages), various types of evolution and various pathophysiological mechanisms. The number of well-studied clinical cases in the literature is surprisingly small. Many of the proposed definitions are not adequate. Although it has been advised that the concept of of progressing stroke be discarded, this advice seems premature considering that it is a common and critical condition and one which has been in fact imperfectly and incompletely investigated. Instead, it would appear better to organize a prospective study with detailed clinical reports, serial CT, angiography, and when possible NMR PET or SPECT and detailed pathological examination of brain and extra-intracranial cerebral arteries. The magnitude of the task is such that a multicenter study would probably be required.