Macrorhabdus ornithogaster, avian gastric yeast, is a common cause of gastrointestinal disease in budgerigars ( Melopsittacus undulatus). To better understand the clinical disease in budgerigars presented in a practice population, we reviewed the occurrence, clinical signs, and treatment success of M ornithogaster disease in budgerigars during a 2.5-year period at the Clinic for Birds and Reptiles, University of Leipzig (Leipzig, Germany). The yeast was diagnosed by microscopic examination of fresh fecal samples. Male budgerigars of all ages were most affected. Most clinical signs in birds with confirmed positive results were nonspecific, except for the occurrence of undigested seeds in the feces. Although radiographic appearance of a dilated proventriculus is indicative of a M ornithogaster infection, it is difficult to recognize because of the small size of the budgerigars. Birds with positive results were treated with amphotericin B (100 mg/kg PO q12h) for 4 weeks. Treatment was stressful for the birds because of the handling required and the long treatment duration, and therapeutic results were unsatisfactory. Therefore, the indications for treatment with amphotericin B should be carefully considered in birds with positive M ornithogaster results. An increased occurrence of the infection in association with other pathogens was detected.