Hoi, I looked at TFile f("/nfs/farm/babar/AWG23/ISL/sx-080702/b0cocktail/output/outputdir/b0cocktail-sp4-old2000-151.root") I dumped all timestamps in that file: void anaVub::dump() { int uid, lid; TTree *t1; t1 = (TTree*)gFile->Get("h1"); t1->SetBranchAddress("upperID", &uid); t1->SetBranchAddress("lowerID", &lid); Int_t nentries = Int_t(t1->GetEntries()); Int_t nb(0), nbytes(0); for (Int_t jentry = 0; jentry < nentries; jentry++) { nb = t1->GetEntry(jentry); nbytes += nb; sprintf(line, "%x:%x ", uid, lid); cout << line << endl; } } root [2] a.dump(); > bla and then I sort and uniq them: shire04>sort bla > bla.sort shire04>uniq bla.sort > bla.uniq shire04>wc bla 2111 2111 27443 bla shire04>wc bla.sort 2111 2111 27443 bla.sort shire04>wc bla.uniq 2111 2111 27443 bla.uniq I do not see duplicate events. Could you maybe provide better evidence, please? Cheers, --U.