A description is provided for Alternaria dianthi. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Dianthus spp., and other members of the Caryophyllaceae including Gypsophila and Saponaria spp. It is occasionally reported from other plants (e.g. Hibiscus esculentus (51, 1025; 42, 655)). DISEASE: Carnation blight. The fungus causes yellowing and necrosis of the host tissue, initially killing the leaves but in severe infections, also the stem and eventually the whole plant. The fungus can persist in the soil, from where it can attack seedlings, usually destroying them rapidly. It also infects the host's flowers, seed capsules and seeds. GEOGRAPHICAL DISTRIBUTION: Africa: Egypt, Malawi, Morocco, Mozambique, South Africa, Tanzania, Zambia, Zimbabwe. Asia: Cyprus, India, Japan, Malaysia, Taiwan, Thailand, Turkey, USSR (Armenia, Republic of Georgia). Australasia & Oceania: Australia (New South Wales, Queensland, South Australia), New Zealand, USA (Hawaii). Europe: Austria, Bulgaria, Czechoslovakia, Denmark, France, Germany, Hungary, Italy, The Netherlands, Norway, Poland, Romania, Spain Sweden, UK, Yugoslavia. North America: Bermuda, Canada, Jamaica, Panama, Puerto Rico, USA. South America: Brazil, Uruguay. TRANSMISSION: Successful growth and sporulation of the fungus requires warm moist conditions (optimal mycelial growth is at ca 20°C), although mycelium can survive at 0°C. Transmission of conidia is usually via wind, seeds or soil. A damp leaf surface is essential for infection.