An open multi-centered veterinary clinical trial, comparing conditions before and after treatment with a herbal preparation, containing the powdered root of Echinacea purpurea, was conducted by 6 practicing veterinarians in Switzerland. The plant-based immune stimulant was administered to 41 dogs with manifestations of chronic and seasonal upper respiratory tract infections, including pharyngitis/tonsillitis, bronchitis and kennel cough. Each animal was at an individual stage of the disease, with various symptoms and different severity scores, at start of treatment. There was no control group. Echinacea powder (1:3) was administered with the food at a dose of 1.0 g/10 kg body weight once daily for 8 weeks. Overall efficacy showed significant improvement for 92% of 39 dogs after 4 weeks of treatment and this was confirmed after 8 weeks. Significant reductions of severity and resolution of typical clinical symptoms, of clear nasal secretions, enlargement of lymph nodes, dry cough, dyspnea and dry lung sounds, were evident after 4 weeks. Only two adverse effects, not suspected to be attributable to the study drug, were recorded. Because quality and stability of the Echinacea powder were defined, using an analytical standard and purity tests, these data suggest, that the Echinacea preparation can be recommended as a well tolerated alternative treatment of canine upper respiratory tract infections.