Abstract A description is provided for Sclerotium cepivorum . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: On onion, chives, garlic, leek, shallot, Allium canadense, A. fistulosum, A. vineale and other species of Allium . Has been recorded on Zephyranthes, Belamcanda chinensis (probably saphrophytic on the latter; 50, 1846) and on linseed, clover, cabbage and tomato by inoculation (49, 720). DISEASE: White rot of onions and their allies. GEOGRAPHICAL DISTRIBUTION: Africa (Egypt, Libya, Rhodesia, S. Africa); Asia (India, Japan, Pakistan); Australasia (Australia, New Zealand); Europe (Azores, Bulgaria, Cyprus, Czechoslovakia, Denmark, Finland, France, Germany, UK, Italy, Netherlands, Norway, Romania, Spain, Sweden, Switzerland, USSR, Yugoslavia); North America (Canada, USA); South America (Argentina, Bolivia, Brazil, Colombia, Peru, Uruguay). (CMI Map 331, ed. 2, 1968). TRANSMISSION: Soil-borne. Inoculum remains viable and capable of reinfecting crops for at least 8 yr (17, 717), and there is a limited amount of saprophytic growth in soil (33, 134; 36, 567). Also dispersed on diseased seedlings and sets and by agricultural practices which disseminate soil particles and refuse from diseased crops; can survive passage through domestic animals (22, 422; 54, 3585).