The finding of bland, sterile vegetations in children with severe tetralogy of Fallot is unexpected, and to our knowledge, has not been reported previously. Eight patients diagnosed with tetralogy between January 1993 and July 1997 had sterile vegetations proven by histological and microbiological evaluation, in their right ventricular outflow tracts. Four of these patients were experiencing severe hyper-cyanotic spells, and four had severely reduced effort tolerance at presentation. They all underwent cardiac catheterization and were submitted for surgical repair. At surgery, the vegetations were thought to be causing further narrowing of the already tight fibrotic infundibular stenosis. Two of these patients had evidence of damaged valves, without evidence of active endocarditis. Although initially sterile, these vegetations, may in some instances, become infected.