Endemic of Corynespora leaf fall disease (CLFD) in rubber plantations sometime change to be explosive on certain clones which commercially planted in large scale in some area such as GT 1 and RRIm 600; while on some susceptible clones CLFD has been known to cause retardation of rubber plant growth until untapped. Some resistant clones in Indonesia and other countries in South East Asia were reported having paradox responses to Corynespora cassiicola, the casual agent of CLFD, in other countries; for example the resistant clone PB 260 was reported to be severely affected in Cote dIvoire. In effort to understand the incidence of CLFD outbreak in plantation, nine isolates of C. cassiicola (eight isolates from North Sumatra Proviince and one isolate from West Java) which originated from rubber clones having differential resistance were tested their specificity by inoculating them on GT 1; while one isolate of C. cassiicola from papaw and two isolates from moderate resistant and susceptible rubber clones were compared each othe by inoculating on PR 303, PB 260 and IRR 100. The results indicated that isolates of C. cassiicola which originated from rubber clones which are resistant to CLF caused high disease severity on GT 1, while isolates from clones which are susceptible for moderate resistant which originated from North Sumatra caused moderate to high disease severity. Light disease severity was caused by isolate from susceptible clone PPN 2444 which originated from West Java Province. On PB 260 isolate of C. cassiicola from papaw can attack with high severity, while two isolates from susceptible clone RRIC 103 and from moderate resistant clone GT 1 caused light severity. High yield clone IRR 100 was lightly attacked by isolate of C. cassiicola which originated from GT 1 and no disease incidence was caused by isolates from papaw or from suscepible clone RRIC 103, so those could be categorized as resistant clone. It was suggested that replanting on rubber growing area which C. cassiicola has been endemic should use clones having wide resistance diversity and the percentage of clones which are moderate resistant should be minimized. On the rubber developing area with vegetation to be hosts for C. cassiicola, it is possible that disease outbreak could be caused by primary inocula come from non-rubber host. Therefore, some resistant clones need to be planted in a small scale trial to precede commercially planting.