Phytophthora capsici is the most important plant parasitic fungus causes stem rot disease in black pepper cultivation in Indonesia. The objective of the present study was to observe morphological variation and virulence of Phytophthora isolated on black pepper from various areas in Indonesia. Fifty isolates of Phytophthora were observed under light microscope. The observed morphological characteristics of each isolate, i.e. sporangiophore branching type, colony type, mating type and shape of sporangium after they were grown in growth medium of V8 juice agar, while length and width of sporangium, length of sporangiophore, and papilla were measured by micrometer. The variation of their virulence was observed by inoculating the hypha of each isolate on detached leaves of black pepper that incubated in damped boxes in room conditions. The width of necrotics were measured with leaf area meter after incubated for four days. The results indicated, those morphological characteristics of the isolates were vary in size, shape, colony pattern, mating type and sporangiophore branching pattern, which those characteristics were belong to P. capsici. Those morphological characteristics were not related with the mating type, isolated plant parts and its geographic distribution. The virulence of the tested isolates were also vary from low to high, and their virulence were also not related with the mating type, isolated plant parts and its geographic distribution.