Background Irrational use of this drug leads to emergence of resistant bacteria and also leads to infections that are worse than the original diagnosed ones. Important concern is the uncertainty of administered antibiotics about whether the quality of a generic medicine is equal to brand name drug; if both brand/generic are bioequivalent, then antibiotic selection should be based on the cost of therapy. Methods The efficacy of seven ceftriaxone brands available at Ambo, Oromia Regional State, Ethiopia, was evaluated by microwell plate diffusion technique against four different bacteria. Results All brands of two concentrations were showed sufficient inhibitory activity against four microorganisms, so they should all be considered as bioequivalence. Among all brands tested, B6 showed higher activity against Escherichia coli American Type Culture Collection (ATCC) 10536, Staphylococcus aureus ATCC 29737 and Pseudomonas aeruginosa ATCC 25619, and B1 showed higher activity against Salmonella typhi ATCC 06775. Interestingly, the concentration C2 (50 μg/ml) of B1-B7 showed equivalent zone of inhibition to that of the standard. ConclusionWe conclude that performance of tested ceftriaxone injectable products were equivalent to the standard. We recommend that the physicians may select the ceftriaxone brand which is low cost in order to reduce the cost of treatment.