AIM:To analyze the lab diagnosis and etiology of infectious endophthalmitis.· METHODS:The medical and microbial records of 36 patients diagnosed with infectious endophthalmitis and 8 patients diagnosed with intraocular lens(IOL)-related inflammation between Nov.1999 and Dec.2009 were retrospectively reviewed for lab diagnosis and etiology.RESULTS:The inflammatory cell counts in all aqueous humor specimens from infectious endophthalmitis patients were more than in all aqueous humor specimens from patients with IOL-related inflammation.Sixteen of the 36 aqueous humor samples(44.4%) and 11 of the 24 vitreous humor samples(45.8%) from infectious endophthalmitis patients showed positive results in smears;while 17 aqueous humor samples(47.2%) and 15 vitreous humor samples(62.5%) from infectious endophthalmitis patients showed positive results in culture.CONCLUSION:The inflammatory cell count may be an important index for infectious endophthalmitis;while,smears can show etiological information earlier.