The effects of temperature and water activity (Aw) were studied on the growth activity of Cladosporium sphaerospermum and C. cladosporioides. High growth was noted in C. sphaerospermum at high temperatures and in C. cladosporioides at low temperatures, but the growth activity of both C. sphaerospermum and C. cladosporioides was similar at 23-30°C. With regard to Aw, growth of C. cladosporioides was greater than that of C. sphaerospermum at 10-23°C. At 32-36°C, higher activities were shown in C. sphaerospermum. C. sphaerospermum and C. cladosporioides showed morphological changes such as dark brown hyphae with thick and cigar shaped cells, .and irregulary swollen cells at low Aw. C. sphaerospermum showed a broader range of growth temperature and Aw than C. cladosporioides.