High breathing frequency, white serous or mucous nasal discharge, cough and dyspnoea are the most common clinical signs of RAO in horses of Slovenia. We found arterial oxygen partial pressure reliable to determine the presence of pulmonary disease. Neutrophilic inflammation has been established in the bronchoalveolar lavage fluid. Computer simulation of the EPR spectra brought us to the conclusion, that neutrophil membrane consists of at least four types of domains. Reduction of the spin probe in neutrophils from BAL is faster in healthy horses then in horses with RAO. Possible reducing agents in neutrophils are oxy-redoxy enzymes, ascorbate and free radicals. With preclinical and clinical studies we succeded to introduce and to evaluate the electrochemotherapy with cisplatin and bleomycin into veterinary medicine. Intratumourally deliver of cisplatin, or in some cases bleomycin and immediately thereafter exposed to electric pulses was used. All studies show that electrochemotherapy with cisplatin or bleomycin is an effective, safe, and simple local treatment of different histological types of cutaneous and subcutaneous tumours in cats, dogs and horses. The advantages of this therapy are its simplicity, short duration of treatment sessions, low chemotherapeutic doses, and insignificant side effects.