A total of 187 dogs, 110 with clinical signs of otitis externa (OE), and 77 without history or clinical signs of OE, were examined microenvironment and microbiological analysis of their ear exudates made. The aural temperature and humidity of 160 dogs were measured. There were no significant differentce between healthy dogs and OE dogs. German shepherd showed relatively lower temperature (p<0.01) and higher humidity (p<0.01). The mean log₁₀ number of microbial organisms of ears of OE dogs (4.16 ± 0.31 cfu/g) was significantly increased, compared to that from the ears of non-OE group (2.55 ± 0.24 cfu/g). Pseudomonas spp. and Proteus spp. were detected only from OE dogs. In addition, three enterotoxigenic Staphylococcus aureus were isolated from ear specimens.