Cephazolin sodium prepared with four different solutions (NaCl 0.9%, Protagent, Liquifilm and phosphate buffer) to be used as eye drops, was evaluated as to its physicochemical features at +4 degrees C, +37 degrees C and at room temperature and its activity in terms of minimal inhibition concentration. In conclusion, cephazolin sodium prepared with artificial tears at acidic pH can be kept for 3 days at room temperature and at +4 degrees C without any loss of its activity.