The objective of the present study was to evaluate the efficacy and safety of the antiparasitic spot-on formulation containing imidacloprid 10%/moxidectin 1% (Advocate, Bayer) in the treatment of natural feline infection with the lungworm Aelurostrongylus abstrusus (Nematoda, Strongylida). The efficacy of Advocate administered once was tested in comparison to a control oral formulation containing fenbendazole 18.75% (Panacur Intervet) administered over three consecutive days based on larvae per gramme of faeces (LPG), measured on days 28 +/- 2 following treatment and compared to counts on days -6 to -2. In total 24 cats treated either with Advocate (n = 12) or with Panacur (n = 12) were included. Mean LPG postbaseline (days 28 +/- 2) were low in both treatment groups, i.e., 0 LPG for Advocate and 1.3 LPG for Panacur. Reduction of post-baseline larval counts showed Advocate (100% reduction) to be superior in efficacy compared to the control product (99.29% reduction). No treated animals showed adverse events. This trial demonstrated that both Advocate spot-on formulation and Panacur oral paste are safe and effective in the treatment of aelurostrongylosis in cats. Future practical perspectives in feline medicine and the major advantages of the spot-on product compared to the oral paste are discussed.