This study examined rates of asymptomatic keratitis in failed full thickness corneal grafts, which were not picked up clinically preoperatively. During a five year period 53 penetrating keratoplasties (PK) were performed for long-standing graft decompensation with stromal opacity and / or graft irregularity. None of the eyes were suspected of infections preoperatively due to lack of pain, redness and tearing. Histological examination and / or cultures of removed corneal buttons confirmed the presence of an infection in seven eyes (13.2%). Preoperative abnormal clinical findings included: epithelial defect (85%), focal whitening of corneal stroma (71%), crystalline keratopathy (14%), and elevated pigmented lesion (14%). Postoperative infectious keratitis was seen in 71% eyes and the same organism was cultured in 80% of eyes as found in the removed corneal buttons. Presence of epithelial defect in failed PK, even without any suggestive symptoms, should raise suspicion of silent infectious keratitis with less virulent organisms and requires sending corneal buttons for microbiology analysis if surgical intervention is opted for.