Abstract A description is provided for Diaporthe citri . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: On Citrus aurantifolia, C. aurantium, C. grandis, C. limon, C. parasisi, C. reticulata and C. sinensis . DISEASE: Melanose of Citrus spp. and stem end rot of the fruit. Symptoms occur on the immature leaves, young branches, stalks and fruit. The very small spots enlarge, become water-soaked, sunken, dark with chlorotic halos and develop raised, corky, superficial, necrotic areas up to 1 mm diam. ; this spotting is frequently very abundant and scar-like, necrotic aggregations are formed; on the fruit the spots are sometimes arranged in rings, lines or curves. Leaves are distorted and may fall prematurely. The small, dying branches bear the same raised spots in which both spore stages are found. Diaporthe citri is one of the citrus pathogens which penetrates the fruit at the stem end and causes a rot in storage (7, 713; 23, 386; 50, 679). GEOGRAPHICAL DISTRIBUTION: Widespread in citrus growing areas (CMI Map 126, ed. 2, 1966). TRANSMISSION: Water-borne through the conidia.