The comparative blood, egg and tissue residues as well as the adverse effects of enrofloxacin represented in Enrotryl and Baytril were investigated in laying hens following repeated oral administration ® ® at a dose rate 10 mg enrofloxacin base /kg b. wt., once daily for 5 consecutive days. Enrofloxacin in both products was microbiologically assayed in blood, eggs and tissues using Bacillus cereus as a test organism. It was completely cleared from blood, egg and all tissue tested on the 5 day after the last oral dose. The effect th of enrofloxacin in the two tested preparations on some blood parameters (glucose, cholesterol, total proteins, urea, creatinine) and blood picture (Hb, PCV%, RBCs and WBCs counts) revealed insignificant changes after discontinuation of drug regimen. From this study it was concluded that the withdrawal time of enrofloxacin in Enrotryl and Baytril in eggs and tissues of laying hens was 5 days and that repeated administration of ® ® enrofloxacin in the form of Enrotryl and Baytril did not induce any adverse effect when used in a therapeutic ® ® regimen.