An ongoing outbreak of Mycoplasma gallisepticum-associated conjunctivitis in house finches (Carpodacus mexicanus) that began in 1994 in the eastern United States has been spreading westward. House finches presenting with the clinical signs of M. gallisepticum-associated conjunctivitis were first seen at the Wildlife Rehabilitation Center of Minnesota (Minnesota, USA) in July of 1996, and 42 cases were admitted from 26 December 1996 to 10 August 1997. A nested PCR was designed for sensitive and specific detection of the presence of the organism. Twelve birds were treated with oral enrofloxacin (15 mg/kg, twice daily for 21 days) and ophthalmic gentamicin (twice daily for 21 days). All treated birds showed resolution of clinical signs. Following treatment, finches were held for up to 6 mo and tested for the presence of M. gallisepticum by culture and nested polymerase chain reaction (PCR). Eight of twelve finches (67%) were positive for M. gallisepticum by nested-PCR and four (33%) were positive by culture. The results suggest that oral enrofloxacin and opthalmic gentamicin are not an effective treatment for the eradication of M. gallisepticum in house finches. Further, the results show that nested PCR is an effective method for detection of M. gallisepticum in house finches and was more sensitive than culture.