Most pet rats have chronic respiratory disease, and end-stage complications are frequently fatal. Drug aerosol delivery in the form of nebulization of antibiotics, expectorants, and bronchodilators is often used as part of their treatment. As rats are obligate nasal breathers, aerosol delivery must be achieved by nasal inhalation, which has the anatomical limitation of a narrower airway lumen. In humans, aerosol delivery of many respiratory drugs is achieved by oral inhalation as it allows administration of very small particles with a concentration loss of only 20% in comparison with 85% by the nasal route. The aim of this pilot study was to determine whether a nebulized fluorescein solution would reach the lungs of rats as no data exists. Ten healthy 13-week-old female Sprague-Dawley rats were nebulized continuously for 15 minutes. The rats were euthanized, and a full postmortem examination was performed. The respiratory tract was sampled, fast-frozen in liquid nitrogen and preserved at -20 degrees C. Slides were examined with a fluorescence microscope to determine the distribution of fluorescein in the respiratory tract. Fluorescence was observed in the entire respiratory tract of all the nebulized rats, showing that nebulization is an efficient way to deliver medication directly into the alveoli.