Анотация: Pseudomonas aeruginosa (P. aeruginosa) infection in ear canals of dogs is associated with severe otitis externa (OE). Traditional use of antibiotics alone or in combination with topical antiseptic solutions to treat Pseudomonas OE is often associated with the development of antibiotic resistance. Tris-EDTA/chlorhexidine solution is very active against several species of gram-positive and gram-negative bacteria in-vitro. Therefore, in-vivo effect of topical antiseptic solution containing Tris-EDTA/ chlorhexidine 0.15 percentage on clinical and microbiological parameters in 18 dogs diagnosed with Pseudomonas- associated OE, with (n=12) or without (n=6) the concomitant use of oral fluoroquinolones, was evaluated over an eight week period. Dogs were evaluated on days 0, 7, 14, 21, 28, 42 and 56. Clinical signs: pain, oedema, erythema and stenosis of the ear canal were evaluated and scored from 0 to 4. Overall combined score including all clinical signs was also calculated to show all clinical signs as an independent variable. Ear canal swabs and scrubs were used to assess for culture and fluoroqinolone sensitivity, parasitological examination and cytological evaluation. Linear mixed effects model and the logistic regression with the random effect were used to evaluate the effect of Tris-EDTA/chlorhexidine (time) and fluoroquinolones treatment on clinical, cytological and bacteriological variables