During a 6-month period, 108 sexually mature stray cats were euthanatized at a humane shelter in Alabama. Aelurostrongylus abstrusus was identified in 20 of the cats (18.5%) by Baermann fecal examination, necropsy, or histologic examination. The Baermann fecal examination was a more sensitive test for aelurostrongylosis than was necropsy or histologic examination. Thoracic radiography was useful in identifying infected cats, but was a less sensitive and more nonspecific method of detection than was the fecal examination. Changes in CBC and serum protein concentrations were not helpful identifying cats with aelurostrongylosis. Six of 17 (35%) heartworm-free, lungworm-infected cats had antibodies to Dirofilaria immitis, as determined by an ELISA method, but none had circulating D immitis antigen, as determined by an ELISA method. Three (2.8%) cats had D immitis. Two of the heartworm-infected cats had no detectable antemortem radiographic or clinicopathologic evidence of the infection. Results of ELISA were positive for antibodies to adult heartworms in 2 cats and for circulating heartworm antigen in 2 cats. One cat that had only one heartworm had no detectable circulating heartworm antigen.