An undescribed graft transmissible disease has been found on Nagami kumquat. Three types of symptoms have been observed: 1) vein clearing on Pineapple sweet orange, Troyer citrange, sour orange, Marsh grapefruit, Orlando tangelo, Dweet tangor and Alemow, but not on Mexican lime, Etrog citron, Cleopatra mandarin, rough lemon, Eureka lemon, Volkamer lemon, trifoliate orange, Nules clementine and Parson's special mandarin; 2) stem pitting on Etrog citron, but not on the other species and hybrids; and 3) graft incompatibility of Nagami kumquat on Troyer citrange, but not on rough lemon. Vein clearing symptoms were more severe in seedlings grown a t 18-25OC than a t 27-32OC. Stem pitting was induced only a t 18-25OC. Some kumquat plants obtained by shoot-tip grafting in vitro were compatible with Troyer citrange, and did not induce vein clearing, but still produced stem pitting. These data suggest the presence of more than one pathogen on the original plants. Preliminary electron microscopy studies have shown the presence of some virus-like particles about 800 nm long in extracts of infected Troyer citrange and sweet orange plants. Diseased kumquats gave negative reactions by ELISA using four different tristeza antisera.